linux/fs/xattr.c

1761 lines
46 KiB

2012-02-07 18:52:57 -08:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
acl: handle idmapped mounts The posix acl permission checking helpers determine whether a caller is privileged over an inode according to the acls associated with the inode. Add helpers that make it possible to handle acls on idmapped mounts. The vfs and the filesystems targeted by this first iteration make use of posix_acl_fix_xattr_from_user() and posix_acl_fix_xattr_to_user() to translate basic posix access and default permissions such as the ACL_USER and ACL_GROUP type according to the initial user namespace (or the superblock's user namespace) to and from the caller's current user namespace. Adapt these two helpers to handle idmapped mounts whereby we either map from or into the mount's user namespace depending on in which direction we're translating. Similarly, cap_convert_nscap() is used by the vfs to translate user namespace and non-user namespace aware filesystem capabilities from the superblock's user namespace to the caller's user namespace. Enable it to handle idmapped mounts by accounting for the mount's user namespace. In addition the fileystems targeted in the first iteration of this patch series make use of the posix_acl_chmod() and, posix_acl_update_mode() helpers. Both helpers perform permission checks on the target inode. Let them handle idmapped mounts. These two helpers are called when posix acls are set by the respective filesystems to handle this case we extend the ->set() method to take an additional user namespace argument to pass the mount's user namespace down. Link: https://lore.kernel.org/r/20210121131959.646623-9-christian.brauner@ubuntu.com Cc: Christoph Hellwig <hch@lst.de> Cc: David Howells <dhowells@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-21 14:19:27 +01:00
Cache xattr security drop check for write v2 Some recent benchmarking on btrfs showed that a major scaling bottleneck on large systems on btrfs is currently the xattr lookup on every write. Why xattr lookup on every write I hear you ask? write wants to drop suid and security related xattrs that could set o capabilities for executables. To do that it currently looks up security.capability on EVERY write (even for non executables) to decide whether to drop it or not. In btrfs this causes an additional tree walk, hitting some per file system locks and quite bad scalability. In a simple read workload on a 8S system I saw over 90% CPU time in spinlocks related to that. Chris Mason tells me this is also a problem in ext4, where it hits the global mbcache lock. This patch adds a simple per inode to avoid this problem. We only do the lookup once per file and then if there is no xattr cache the decision. All xattr changes clear the flag. I also used the same flag to avoid the suid check, although that one is pretty cheap. A file system can also set this flag when it creates the inode, if it has a cheap way to do so. This is done for some common file systems in followon patches. With this patch a major part of the lock contention disappears for btrfs. Some testing on smaller systems didn't show significant performance changes, but at least it helps the larger systems and is generally more efficient. v2: Rename is_sgid. add file system helper. Cc: chris.mason@oracle.com Cc: josef@redhat.com Cc: viro@zeniv.linux.org.uk Cc: agruen@linbit.com Cc: Serge E. Hallyn <serue@us.ibm.com> Signed-off-by: Andi Kleen <ak@linux.intel.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-05-28 08:25:51 -07:00
Cache xattr security drop check for write v2 Some recent benchmarking on btrfs showed that a major scaling bottleneck on large systems on btrfs is currently the xattr lookup on every write. Why xattr lookup on every write I hear you ask? write wants to drop suid and security related xattrs that could set o capabilities for executables. To do that it currently looks up security.capability on EVERY write (even for non executables) to decide whether to drop it or not. In btrfs this causes an additional tree walk, hitting some per file system locks and quite bad scalability. In a simple read workload on a 8S system I saw over 90% CPU time in spinlocks related to that. Chris Mason tells me this is also a problem in ext4, where it hits the global mbcache lock. This patch adds a simple per inode to avoid this problem. We only do the lookup once per file and then if there is no xattr cache the decision. All xattr changes clear the flag. I also used the same flag to avoid the suid check, although that one is pretty cheap. A file system can also set this flag when it creates the inode, if it has a cheap way to do so. This is done for some common file systems in followon patches. With this patch a major part of the lock contention disappears for btrfs. Some testing on smaller systems didn't show significant performance changes, but at least it helps the larger systems and is generally more efficient. v2: Rename is_sgid. add file system helper. Cc: chris.mason@oracle.com Cc: josef@redhat.com Cc: viro@zeniv.linux.org.uk Cc: agruen@linbit.com Cc: Serge E. Hallyn <serue@us.ibm.com> Signed-off-by: Andi Kleen <ak@linux.intel.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-05-28 08:25:51 -07:00
fs/xattr.c: fix kernel-doc warnings for setxattr & removexattr Fix kernel-doc warnings in fs/xattr.c: ../fs/xattr.c:251: warning: Function parameter or member 'dentry' not described in '__vfs_setxattr_locked' ../fs/xattr.c:251: warning: Function parameter or member 'name' not described in '__vfs_setxattr_locked' ../fs/xattr.c:251: warning: Function parameter or member 'value' not described in '__vfs_setxattr_locked' ../fs/xattr.c:251: warning: Function parameter or member 'size' not described in '__vfs_setxattr_locked' ../fs/xattr.c:251: warning: Function parameter or member 'flags' not described in '__vfs_setxattr_locked' ../fs/xattr.c:251: warning: Function parameter or member 'delegated_inode' not described in '__vfs_setxattr_locked' ../fs/xattr.c:458: warning: Function parameter or member 'dentry' not described in '__vfs_removexattr_locked' ../fs/xattr.c:458: warning: Function parameter or member 'name' not described in '__vfs_removexattr_locked' ../fs/xattr.c:458: warning: Function parameter or member 'delegated_inode' not described in '__vfs_removexattr_locked' Fixes: 08b5d5014a27 ("xattr: break delegations in {set,remove}xattr") Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Frank van der Linden <fllinden@amazon.com> Cc: Chuck Lever <chuck.lever@oracle.com> Link: http://lkml.kernel.org/r/7a3dd5a2-5787-adf3-d525-c203f9910ec4@infradead.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-10-13 16:48:27 -07:00
fs/xattr.c: fix kernel-doc warnings for setxattr & removexattr Fix kernel-doc warnings in fs/xattr.c: ../fs/xattr.c:251: warning: Function parameter or member 'dentry' not described in '__vfs_setxattr_locked' ../fs/xattr.c:251: warning: Function parameter or member 'name' not described in '__vfs_setxattr_locked' ../fs/xattr.c:251: warning: Function parameter or member 'value' not described in '__vfs_setxattr_locked' ../fs/xattr.c:251: warning: Function parameter or member 'size' not described in '__vfs_setxattr_locked' ../fs/xattr.c:251: warning: Function parameter or member 'flags' not described in '__vfs_setxattr_locked' ../fs/xattr.c:251: warning: Function parameter or member 'delegated_inode' not described in '__vfs_setxattr_locked' ../fs/xattr.c:458: warning: Function parameter or member 'dentry' not described in '__vfs_removexattr_locked' ../fs/xattr.c:458: warning: Function parameter or member 'name' not described in '__vfs_removexattr_locked' ../fs/xattr.c:458: warning: Function parameter or member 'delegated_inode' not described in '__vfs_removexattr_locked' Fixes: 08b5d5014a27 ("xattr: break delegations in {set,remove}xattr") Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Frank van der Linden <fllinden@amazon.com> Cc: Chuck Lever <chuck.lever@oracle.com> Link: http://lkml.kernel.org/r/7a3dd5a2-5787-adf3-d525-c203f9910ec4@infradead.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-10-13 16:48:27 -07:00
commoncap: handle idmapped mounts When interacting with user namespace and non-user namespace aware filesystem capabilities the vfs will perform various security checks to determine whether or not the filesystem capabilities can be used by the caller, whether they need to be removed and so on. The main infrastructure for this resides in the capability codepaths but they are called through the LSM security infrastructure even though they are not technically an LSM or optional. This extends the existing security hooks security_inode_removexattr(), security_inode_killpriv(), security_inode_getsecurity() to pass down the mount's user namespace and makes them aware of idmapped mounts. In order to actually get filesystem capabilities from disk the capability infrastructure exposes the get_vfs_caps_from_disk() helper. For user namespace aware filesystem capabilities a root uid is stored alongside the capabilities. In order to determine whether the caller can make use of the filesystem capability or whether it needs to be ignored it is translated according to the superblock's user namespace. If it can be translated to uid 0 according to that id mapping the caller can use the filesystem capabilities stored on disk. If we are accessing the inode that holds the filesystem capabilities through an idmapped mount we map the root uid according to the mount's user namespace. Afterwards the checks are identical to non-idmapped mounts: reading filesystem caps from disk enforces that the root uid associated with the filesystem capability must have a mapping in the superblock's user namespace and that the caller is either in the same user namespace or is a descendant of the superblock's user namespace. For filesystems that are mountable inside user namespace the caller can just mount the filesystem and won't usually need to idmap it. If they do want to idmap it they can create an idmapped mount and mark it with a user namespace they created and which is thus a descendant of s_user_ns. For filesystems that are not mountable inside user namespaces the descendant rule is trivially true because the s_user_ns will be the initial user namespace. If the initial user namespace is passed nothing changes so non-idmapped mounts will see identical behavior as before. Link: https://lore.kernel.org/r/20210121131959.646623-11-christian.brauner@ubuntu.com Cc: Christoph Hellwig <hch@lst.de> Cc: David Howells <dhowells@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig <hch@lst.de> Acked-by: James Morris <jamorris@linux.microsoft.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-21 14:19:29 +01:00
commoncap: handle idmapped mounts When interacting with user namespace and non-user namespace aware filesystem capabilities the vfs will perform various security checks to determine whether or not the filesystem capabilities can be used by the caller, whether they need to be removed and so on. The main infrastructure for this resides in the capability codepaths but they are called through the LSM security infrastructure even though they are not technically an LSM or optional. This extends the existing security hooks security_inode_removexattr(), security_inode_killpriv(), security_inode_getsecurity() to pass down the mount's user namespace and makes them aware of idmapped mounts. In order to actually get filesystem capabilities from disk the capability infrastructure exposes the get_vfs_caps_from_disk() helper. For user namespace aware filesystem capabilities a root uid is stored alongside the capabilities. In order to determine whether the caller can make use of the filesystem capability or whether it needs to be ignored it is translated according to the superblock's user namespace. If it can be translated to uid 0 according to that id mapping the caller can use the filesystem capabilities stored on disk. If we are accessing the inode that holds the filesystem capabilities through an idmapped mount we map the root uid according to the mount's user namespace. Afterwards the checks are identical to non-idmapped mounts: reading filesystem caps from disk enforces that the root uid associated with the filesystem capability must have a mapping in the superblock's user namespace and that the caller is either in the same user namespace or is a descendant of the superblock's user namespace. For filesystems that are mountable inside user namespace the caller can just mount the filesystem and won't usually need to idmap it. If they do want to idmap it they can create an idmapped mount and mark it with a user namespace they created and which is thus a descendant of s_user_ns. For filesystems that are not mountable inside user namespaces the descendant rule is trivially true because the s_user_ns will be the initial user namespace. If the initial user namespace is passed nothing changes so non-idmapped mounts will see identical behavior as before. Link: https://lore.kernel.org/r/20210121131959.646623-11-christian.brauner@ubuntu.com Cc: Christoph Hellwig <hch@lst.de> Cc: David Howells <dhowells@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig <hch@lst.de> Acked-by: James Morris <jamorris@linux.microsoft.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-21 14:19:29 +01:00
commoncap: handle idmapped mounts When interacting with user namespace and non-user namespace aware filesystem capabilities the vfs will perform various security checks to determine whether or not the filesystem capabilities can be used by the caller, whether they need to be removed and so on. The main infrastructure for this resides in the capability codepaths but they are called through the LSM security infrastructure even though they are not technically an LSM or optional. This extends the existing security hooks security_inode_removexattr(), security_inode_killpriv(), security_inode_getsecurity() to pass down the mount's user namespace and makes them aware of idmapped mounts. In order to actually get filesystem capabilities from disk the capability infrastructure exposes the get_vfs_caps_from_disk() helper. For user namespace aware filesystem capabilities a root uid is stored alongside the capabilities. In order to determine whether the caller can make use of the filesystem capability or whether it needs to be ignored it is translated according to the superblock's user namespace. If it can be translated to uid 0 according to that id mapping the caller can use the filesystem capabilities stored on disk. If we are accessing the inode that holds the filesystem capabilities through an idmapped mount we map the root uid according to the mount's user namespace. Afterwards the checks are identical to non-idmapped mounts: reading filesystem caps from disk enforces that the root uid associated with the filesystem capability must have a mapping in the superblock's user namespace and that the caller is either in the same user namespace or is a descendant of the superblock's user namespace. For filesystems that are mountable inside user namespace the caller can just mount the filesystem and won't usually need to idmap it. If they do want to idmap it they can create an idmapped mount and mark it with a user namespace they created and which is thus a descendant of s_user_ns. For filesystems that are not mountable inside user namespaces the descendant rule is trivially true because the s_user_ns will be the initial user namespace. If the initial user namespace is passed nothing changes so non-idmapped mounts will see identical behavior as before. Link: https://lore.kernel.org/r/20210121131959.646623-11-christian.brauner@ubuntu.com Cc: Christoph Hellwig <hch@lst.de> Cc: David Howells <dhowells@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig <hch@lst.de> Acked-by: James Morris <jamorris@linux.microsoft.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-21 14:19:29 +01:00
commoncap: handle idmapped mounts When interacting with user namespace and non-user namespace aware filesystem capabilities the vfs will perform various security checks to determine whether or not the filesystem capabilities can be used by the caller, whether they need to be removed and so on. The main infrastructure for this resides in the capability codepaths but they are called through the LSM security infrastructure even though they are not technically an LSM or optional. This extends the existing security hooks security_inode_removexattr(), security_inode_killpriv(), security_inode_getsecurity() to pass down the mount's user namespace and makes them aware of idmapped mounts. In order to actually get filesystem capabilities from disk the capability infrastructure exposes the get_vfs_caps_from_disk() helper. For user namespace aware filesystem capabilities a root uid is stored alongside the capabilities. In order to determine whether the caller can make use of the filesystem capability or whether it needs to be ignored it is translated according to the superblock's user namespace. If it can be translated to uid 0 according to that id mapping the caller can use the filesystem capabilities stored on disk. If we are accessing the inode that holds the filesystem capabilities through an idmapped mount we map the root uid according to the mount's user namespace. Afterwards the checks are identical to non-idmapped mounts: reading filesystem caps from disk enforces that the root uid associated with the filesystem capability must have a mapping in the superblock's user namespace and that the caller is either in the same user namespace or is a descendant of the superblock's user namespace. For filesystems that are mountable inside user namespace the caller can just mount the filesystem and won't usually need to idmap it. If they do want to idmap it they can create an idmapped mount and mark it with a user namespace they created and which is thus a descendant of s_user_ns. For filesystems that are not mountable inside user namespaces the descendant rule is trivially true because the s_user_ns will be the initial user namespace. If the initial user namespace is passed nothing changes so non-idmapped mounts will see identical behavior as before. Link: https://lore.kernel.org/r/20210121131959.646623-11-christian.brauner@ubuntu.com Cc: Christoph Hellwig <hch@lst.de> Cc: David Howells <dhowells@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig <hch@lst.de> Acked-by: James Morris <jamorris@linux.microsoft.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-21 14:19:29 +01:00
commoncap: handle idmapped mounts When interacting with user namespace and non-user namespace aware filesystem capabilities the vfs will perform various security checks to determine whether or not the filesystem capabilities can be used by the caller, whether they need to be removed and so on. The main infrastructure for this resides in the capability codepaths but they are called through the LSM security infrastructure even though they are not technically an LSM or optional. This extends the existing security hooks security_inode_removexattr(), security_inode_killpriv(), security_inode_getsecurity() to pass down the mount's user namespace and makes them aware of idmapped mounts. In order to actually get filesystem capabilities from disk the capability infrastructure exposes the get_vfs_caps_from_disk() helper. For user namespace aware filesystem capabilities a root uid is stored alongside the capabilities. In order to determine whether the caller can make use of the filesystem capability or whether it needs to be ignored it is translated according to the superblock's user namespace. If it can be translated to uid 0 according to that id mapping the caller can use the filesystem capabilities stored on disk. If we are accessing the inode that holds the filesystem capabilities through an idmapped mount we map the root uid according to the mount's user namespace. Afterwards the checks are identical to non-idmapped mounts: reading filesystem caps from disk enforces that the root uid associated with the filesystem capability must have a mapping in the superblock's user namespace and that the caller is either in the same user namespace or is a descendant of the superblock's user namespace. For filesystems that are mountable inside user namespace the caller can just mount the filesystem and won't usually need to idmap it. If they do want to idmap it they can create an idmapped mount and mark it with a user namespace they created and which is thus a descendant of s_user_ns. For filesystems that are not mountable inside user namespaces the descendant rule is trivially true because the s_user_ns will be the initial user namespace. If the initial user namespace is passed nothing changes so non-idmapped mounts will see identical behavior as before. Link: https://lore.kernel.org/r/20210121131959.646623-11-christian.brauner@ubuntu.com Cc: Christoph Hellwig <hch@lst.de> Cc: David Howells <dhowells@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig <hch@lst.de> Acked-by: James Morris <jamorris@linux.microsoft.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-21 14:19:29 +01:00
fs/xattr.c: fix kernel-doc warnings for setxattr & removexattr Fix kernel-doc warnings in fs/xattr.c: ../fs/xattr.c:251: warning: Function parameter or member 'dentry' not described in '__vfs_setxattr_locked' ../fs/xattr.c:251: warning: Function parameter or member 'name' not described in '__vfs_setxattr_locked' ../fs/xattr.c:251: warning: Function parameter or member 'value' not described in '__vfs_setxattr_locked' ../fs/xattr.c:251: warning: Function parameter or member 'size' not described in '__vfs_setxattr_locked' ../fs/xattr.c:251: warning: Function parameter or member 'flags' not described in '__vfs_setxattr_locked' ../fs/xattr.c:251: warning: Function parameter or member 'delegated_inode' not described in '__vfs_setxattr_locked' ../fs/xattr.c:458: warning: Function parameter or member 'dentry' not described in '__vfs_removexattr_locked' ../fs/xattr.c:458: warning: Function parameter or member 'name' not described in '__vfs_removexattr_locked' ../fs/xattr.c:458: warning: Function parameter or member 'delegated_inode' not described in '__vfs_removexattr_locked' Fixes: 08b5d5014a27 ("xattr: break delegations in {set,remove}xattr") Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Frank van der Linden <fllinden@amazon.com> Cc: Chuck Lever <chuck.lever@oracle.com> Link: http://lkml.kernel.org/r/7a3dd5a2-5787-adf3-d525-c203f9910ec4@infradead.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-10-13 16:48:27 -07:00
fs/xattr.c: fix kernel-doc warnings for setxattr & removexattr Fix kernel-doc warnings in fs/xattr.c: ../fs/xattr.c:251: warning: Function parameter or member 'dentry' not described in '__vfs_setxattr_locked' ../fs/xattr.c:251: warning: Function parameter or member 'name' not described in '__vfs_setxattr_locked' ../fs/xattr.c:251: warning: Function parameter or member 'value' not described in '__vfs_setxattr_locked' ../fs/xattr.c:251: warning: Function parameter or member 'size' not described in '__vfs_setxattr_locked' ../fs/xattr.c:251: warning: Function parameter or member 'flags' not described in '__vfs_setxattr_locked' ../fs/xattr.c:251: warning: Function parameter or member 'delegated_inode' not described in '__vfs_setxattr_locked' ../fs/xattr.c:458: warning: Function parameter or member 'dentry' not described in '__vfs_removexattr_locked' ../fs/xattr.c:458: warning: Function parameter or member 'name' not described in '__vfs_removexattr_locked' ../fs/xattr.c:458: warning: Function parameter or member 'delegated_inode' not described in '__vfs_removexattr_locked' Fixes: 08b5d5014a27 ("xattr: break delegations in {set,remove}xattr") Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Frank van der Linden <fllinden@amazon.com> Cc: Chuck Lever <chuck.lever@oracle.com> Link: http://lkml.kernel.org/r/7a3dd5a2-5787-adf3-d525-c203f9910ec4@infradead.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-10-13 16:48:27 -07:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
vfs: Fix potential circular locking through setxattr() and removexattr() When using cachefiles, lockdep may emit something similar to the circular locking dependency notice below. The problem appears to stem from the following: (1) Cachefiles manipulates xattrs on the files in its cache when called from ->writepages(). (2) The setxattr() and removexattr() system call handlers get the name (and value) from userspace after taking the sb_writers lock, putting accesses of the vma->vm_lock and mm->mmap_lock inside of that. (3) The afs filesystem uses a per-inode lock to prevent multiple revalidation RPCs and in writeback vs truncate to prevent parallel operations from deadlocking against the server on one side and local page locks on the other. Fix this by moving the getting of the name and value in {get,remove}xattr() outside of the sb_writers lock. This also has the minor benefits that we don't need to reget these in the event of a retry and we never try to take the sb_writers lock in the event we can't pull the name and value into the kernel. Alternative approaches that might fix this include moving the dispatch of a write to the cache off to a workqueue or trying to do without the validation lock in afs. Note that this might also affect other filesystems that use netfslib and/or cachefiles. ====================================================== WARNING: possible circular locking dependency detected 6.10.0-build2+ #956 Not tainted ------------------------------------------------------ fsstress/6050 is trying to acquire lock: ffff888138fd82f0 (mapping.invalidate_lock#3){++++}-{3:3}, at: filemap_fault+0x26e/0x8b0 but task is already holding lock: ffff888113f26d18 (&vma->vm_lock->lock){++++}-{3:3}, at: lock_vma_under_rcu+0x165/0x250 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #4 (&vma->vm_lock->lock){++++}-{3:3}: __lock_acquire+0xaf0/0xd80 lock_acquire.part.0+0x103/0x280 down_write+0x3b/0x50 vma_start_write+0x6b/0xa0 vma_link+0xcc/0x140 insert_vm_struct+0xb7/0xf0 alloc_bprm+0x2c1/0x390 kernel_execve+0x65/0x1a0 call_usermodehelper_exec_async+0x14d/0x190 ret_from_fork+0x24/0x40 ret_from_fork_asm+0x1a/0x30 -> #3 (&mm->mmap_lock){++++}-{3:3}: __lock_acquire+0xaf0/0xd80 lock_acquire.part.0+0x103/0x280 __might_fault+0x7c/0xb0 strncpy_from_user+0x25/0x160 removexattr+0x7f/0x100 __do_sys_fremovexattr+0x7e/0xb0 do_syscall_64+0x9f/0x100 entry_SYSCALL_64_after_hwframe+0x76/0x7e -> #2 (sb_writers#14){.+.+}-{0:0}: __lock_acquire+0xaf0/0xd80 lock_acquire.part.0+0x103/0x280 percpu_down_read+0x3c/0x90 vfs_iocb_iter_write+0xe9/0x1d0 __cachefiles_write+0x367/0x430 cachefiles_issue_write+0x299/0x2f0 netfs_advance_write+0x117/0x140 netfs_write_folio.isra.0+0x5ca/0x6e0 netfs_writepages+0x230/0x2f0 afs_writepages+0x4d/0x70 do_writepages+0x1e8/0x3e0 filemap_fdatawrite_wbc+0x84/0xa0 __filemap_fdatawrite_range+0xa8/0xf0 file_write_and_wait_range+0x59/0x90 afs_release+0x10f/0x270 __fput+0x25f/0x3d0 __do_sys_close+0x43/0x70 do_syscall_64+0x9f/0x100 entry_SYSCALL_64_after_hwframe+0x76/0x7e -> #1 (&vnode->validate_lock){++++}-{3:3}: __lock_acquire+0xaf0/0xd80 lock_acquire.part.0+0x103/0x280 down_read+0x95/0x200 afs_writepages+0x37/0x70 do_writepages+0x1e8/0x3e0 filemap_fdatawrite_wbc+0x84/0xa0 filemap_invalidate_inode+0x167/0x1e0 netfs_unbuffered_write_iter+0x1bd/0x2d0 vfs_write+0x22e/0x320 ksys_write+0xbc/0x130 do_syscall_64+0x9f/0x100 entry_SYSCALL_64_after_hwframe+0x76/0x7e -> #0 (mapping.invalidate_lock#3){++++}-{3:3}: check_noncircular+0x119/0x160 check_prev_add+0x195/0x430 __lock_acquire+0xaf0/0xd80 lock_acquire.part.0+0x103/0x280 down_read+0x95/0x200 filemap_fault+0x26e/0x8b0 __do_fault+0x57/0xd0 do_pte_missing+0x23b/0x320 __handle_mm_fault+0x2d4/0x320 handle_mm_fault+0x14f/0x260 do_user_addr_fault+0x2a2/0x500 exc_page_fault+0x71/0x90 asm_exc_page_fault+0x22/0x30 other info that might help us debug this: Chain exists of: mapping.invalidate_lock#3 --> &mm->mmap_lock --> &vma->vm_lock->lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- rlock(&vma->vm_lock->lock); lock(&mm->mmap_lock); lock(&vma->vm_lock->lock); rlock(mapping.invalidate_lock#3); *** DEADLOCK *** 1 lock held by fsstress/6050: #0: ffff888113f26d18 (&vma->vm_lock->lock){++++}-{3:3}, at: lock_vma_under_rcu+0x165/0x250 stack backtrace: CPU: 0 PID: 6050 Comm: fsstress Not tainted 6.10.0-build2+ #956 Hardware name: ASUS All Series/H97-PLUS, BIOS 2306 10/09/2014 Call Trace: <TASK> dump_stack_lvl+0x57/0x80 check_noncircular+0x119/0x160 ? queued_spin_lock_slowpath+0x4be/0x510 ? __pfx_check_noncircular+0x10/0x10 ? __pfx_queued_spin_lock_slowpath+0x10/0x10 ? mark_lock+0x47/0x160 ? init_chain_block+0x9c/0xc0 ? add_chain_block+0x84/0xf0 check_prev_add+0x195/0x430 __lock_acquire+0xaf0/0xd80 ? __pfx___lock_acquire+0x10/0x10 ? __lock_release.isra.0+0x13b/0x230 lock_acquire.part.0+0x103/0x280 ? filemap_fault+0x26e/0x8b0 ? __pfx_lock_acquire.part.0+0x10/0x10 ? rcu_is_watching+0x34/0x60 ? lock_acquire+0xd7/0x120 down_read+0x95/0x200 ? filemap_fault+0x26e/0x8b0 ? __pfx_down_read+0x10/0x10 ? __filemap_get_folio+0x25/0x1a0 filemap_fault+0x26e/0x8b0 ? __pfx_filemap_fault+0x10/0x10 ? find_held_lock+0x7c/0x90 ? __pfx___lock_release.isra.0+0x10/0x10 ? __pte_offset_map+0x99/0x110 __do_fault+0x57/0xd0 do_pte_missing+0x23b/0x320 __handle_mm_fault+0x2d4/0x320 ? __pfx___handle_mm_fault+0x10/0x10 handle_mm_fault+0x14f/0x260 do_user_addr_fault+0x2a2/0x500 exc_page_fault+0x71/0x90 asm_exc_page_fault+0x22/0x30 Signed-off-by: David Howells <dhowells@redhat.com> Link: https://lore.kernel.org/r/2136178.1721725194@warthog.procyon.org.uk cc: Alexander Viro <viro@zeniv.linux.org.uk> cc: Christian Brauner <brauner@kernel.org> cc: Jan Kara <jack@suse.cz> cc: Jeff Layton <jlayton@kernel.org> cc: Gao Xiang <xiang@kernel.org> cc: Matthew Wilcox <willy@infradead.org> cc: netfs@lists.linux.dev cc: linux-erofs@lists.ozlabs.org cc: linux-fsdevel@vger.kernel.org [brauner: fix minor issues] Signed-off-by: Christian Brauner <brauner@kernel.org>
2024-07-23 09:59:54 +01:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
treewide: use kv[mz]alloc* rather than opencoded variants There are many code paths opencoding kvmalloc. Let's use the helper instead. The main difference to kvmalloc is that those users are usually not considering all the aspects of the memory allocator. E.g. allocation requests <= 32kB (with 4kB pages) are basically never failing and invoke OOM killer to satisfy the allocation. This sounds too disruptive for something that has a reasonable fallback - the vmalloc. On the other hand those requests might fallback to vmalloc even when the memory allocator would succeed after several more reclaim/compaction attempts previously. There is no guarantee something like that happens though. This patch converts many of those places to kv[mz]alloc* helpers because they are more conservative. Link: http://lkml.kernel.org/r/20170306103327.2766-2-mhocko@kernel.org Signed-off-by: Michal Hocko <mhocko@suse.com> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> # Xen bits Acked-by: Kees Cook <keescook@chromium.org> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Andreas Dilger <andreas.dilger@intel.com> # Lustre Acked-by: Christian Borntraeger <borntraeger@de.ibm.com> # KVM/s390 Acked-by: Dan Williams <dan.j.williams@intel.com> # nvdim Acked-by: David Sterba <dsterba@suse.com> # btrfs Acked-by: Ilya Dryomov <idryomov@gmail.com> # Ceph Acked-by: Tariq Toukan <tariqt@mellanox.com> # mlx4 Acked-by: Leon Romanovsky <leonro@mellanox.com> # mlx5 Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: Anton Vorontsov <anton@enomsg.org> Cc: Colin Cross <ccross@android.com> Cc: Tony Luck <tony.luck@intel.com> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> Cc: Ben Skeggs <bskeggs@redhat.com> Cc: Kent Overstreet <kent.overstreet@gmail.com> Cc: Santosh Raspatur <santosh@chelsio.com> Cc: Hariprasad S <hariprasad@chelsio.com> Cc: Yishai Hadas <yishaih@mellanox.com> Cc: Oleg Drokin <oleg.drokin@intel.com> Cc: "Yan, Zheng" <zyan@redhat.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: David Miller <davem@davemloft.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-05-08 15:57:27 -07:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
treewide: use kv[mz]alloc* rather than opencoded variants There are many code paths opencoding kvmalloc. Let's use the helper instead. The main difference to kvmalloc is that those users are usually not considering all the aspects of the memory allocator. E.g. allocation requests <= 32kB (with 4kB pages) are basically never failing and invoke OOM killer to satisfy the allocation. This sounds too disruptive for something that has a reasonable fallback - the vmalloc. On the other hand those requests might fallback to vmalloc even when the memory allocator would succeed after several more reclaim/compaction attempts previously. There is no guarantee something like that happens though. This patch converts many of those places to kv[mz]alloc* helpers because they are more conservative. Link: http://lkml.kernel.org/r/20170306103327.2766-2-mhocko@kernel.org Signed-off-by: Michal Hocko <mhocko@suse.com> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> # Xen bits Acked-by: Kees Cook <keescook@chromium.org> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Andreas Dilger <andreas.dilger@intel.com> # Lustre Acked-by: Christian Borntraeger <borntraeger@de.ibm.com> # KVM/s390 Acked-by: Dan Williams <dan.j.williams@intel.com> # nvdim Acked-by: David Sterba <dsterba@suse.com> # btrfs Acked-by: Ilya Dryomov <idryomov@gmail.com> # Ceph Acked-by: Tariq Toukan <tariqt@mellanox.com> # mlx4 Acked-by: Leon Romanovsky <leonro@mellanox.com> # mlx5 Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: Anton Vorontsov <anton@enomsg.org> Cc: Colin Cross <ccross@android.com> Cc: Tony Luck <tony.luck@intel.com> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> Cc: Ben Skeggs <bskeggs@redhat.com> Cc: Kent Overstreet <kent.overstreet@gmail.com> Cc: Santosh Raspatur <santosh@chelsio.com> Cc: Hariprasad S <hariprasad@chelsio.com> Cc: Yishai Hadas <yishaih@mellanox.com> Cc: Oleg Drokin <oleg.drokin@intel.com> Cc: "Yan, Zheng" <zyan@redhat.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: David Miller <davem@davemloft.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-05-08 15:57:27 -07:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
vfs: Fix potential circular locking through setxattr() and removexattr() When using cachefiles, lockdep may emit something similar to the circular locking dependency notice below. The problem appears to stem from the following: (1) Cachefiles manipulates xattrs on the files in its cache when called from ->writepages(). (2) The setxattr() and removexattr() system call handlers get the name (and value) from userspace after taking the sb_writers lock, putting accesses of the vma->vm_lock and mm->mmap_lock inside of that. (3) The afs filesystem uses a per-inode lock to prevent multiple revalidation RPCs and in writeback vs truncate to prevent parallel operations from deadlocking against the server on one side and local page locks on the other. Fix this by moving the getting of the name and value in {get,remove}xattr() outside of the sb_writers lock. This also has the minor benefits that we don't need to reget these in the event of a retry and we never try to take the sb_writers lock in the event we can't pull the name and value into the kernel. Alternative approaches that might fix this include moving the dispatch of a write to the cache off to a workqueue or trying to do without the validation lock in afs. Note that this might also affect other filesystems that use netfslib and/or cachefiles. ====================================================== WARNING: possible circular locking dependency detected 6.10.0-build2+ #956 Not tainted ------------------------------------------------------ fsstress/6050 is trying to acquire lock: ffff888138fd82f0 (mapping.invalidate_lock#3){++++}-{3:3}, at: filemap_fault+0x26e/0x8b0 but task is already holding lock: ffff888113f26d18 (&vma->vm_lock->lock){++++}-{3:3}, at: lock_vma_under_rcu+0x165/0x250 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #4 (&vma->vm_lock->lock){++++}-{3:3}: __lock_acquire+0xaf0/0xd80 lock_acquire.part.0+0x103/0x280 down_write+0x3b/0x50 vma_start_write+0x6b/0xa0 vma_link+0xcc/0x140 insert_vm_struct+0xb7/0xf0 alloc_bprm+0x2c1/0x390 kernel_execve+0x65/0x1a0 call_usermodehelper_exec_async+0x14d/0x190 ret_from_fork+0x24/0x40 ret_from_fork_asm+0x1a/0x30 -> #3 (&mm->mmap_lock){++++}-{3:3}: __lock_acquire+0xaf0/0xd80 lock_acquire.part.0+0x103/0x280 __might_fault+0x7c/0xb0 strncpy_from_user+0x25/0x160 removexattr+0x7f/0x100 __do_sys_fremovexattr+0x7e/0xb0 do_syscall_64+0x9f/0x100 entry_SYSCALL_64_after_hwframe+0x76/0x7e -> #2 (sb_writers#14){.+.+}-{0:0}: __lock_acquire+0xaf0/0xd80 lock_acquire.part.0+0x103/0x280 percpu_down_read+0x3c/0x90 vfs_iocb_iter_write+0xe9/0x1d0 __cachefiles_write+0x367/0x430 cachefiles_issue_write+0x299/0x2f0 netfs_advance_write+0x117/0x140 netfs_write_folio.isra.0+0x5ca/0x6e0 netfs_writepages+0x230/0x2f0 afs_writepages+0x4d/0x70 do_writepages+0x1e8/0x3e0 filemap_fdatawrite_wbc+0x84/0xa0 __filemap_fdatawrite_range+0xa8/0xf0 file_write_and_wait_range+0x59/0x90 afs_release+0x10f/0x270 __fput+0x25f/0x3d0 __do_sys_close+0x43/0x70 do_syscall_64+0x9f/0x100 entry_SYSCALL_64_after_hwframe+0x76/0x7e -> #1 (&vnode->validate_lock){++++}-{3:3}: __lock_acquire+0xaf0/0xd80 lock_acquire.part.0+0x103/0x280 down_read+0x95/0x200 afs_writepages+0x37/0x70 do_writepages+0x1e8/0x3e0 filemap_fdatawrite_wbc+0x84/0xa0 filemap_invalidate_inode+0x167/0x1e0 netfs_unbuffered_write_iter+0x1bd/0x2d0 vfs_write+0x22e/0x320 ksys_write+0xbc/0x130 do_syscall_64+0x9f/0x100 entry_SYSCALL_64_after_hwframe+0x76/0x7e -> #0 (mapping.invalidate_lock#3){++++}-{3:3}: check_noncircular+0x119/0x160 check_prev_add+0x195/0x430 __lock_acquire+0xaf0/0xd80 lock_acquire.part.0+0x103/0x280 down_read+0x95/0x200 filemap_fault+0x26e/0x8b0 __do_fault+0x57/0xd0 do_pte_missing+0x23b/0x320 __handle_mm_fault+0x2d4/0x320 handle_mm_fault+0x14f/0x260 do_user_addr_fault+0x2a2/0x500 exc_page_fault+0x71/0x90 asm_exc_page_fault+0x22/0x30 other info that might help us debug this: Chain exists of: mapping.invalidate_lock#3 --> &mm->mmap_lock --> &vma->vm_lock->lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- rlock(&vma->vm_lock->lock); lock(&mm->mmap_lock); lock(&vma->vm_lock->lock); rlock(mapping.invalidate_lock#3); *** DEADLOCK *** 1 lock held by fsstress/6050: #0: ffff888113f26d18 (&vma->vm_lock->lock){++++}-{3:3}, at: lock_vma_under_rcu+0x165/0x250 stack backtrace: CPU: 0 PID: 6050 Comm: fsstress Not tainted 6.10.0-build2+ #956 Hardware name: ASUS All Series/H97-PLUS, BIOS 2306 10/09/2014 Call Trace: <TASK> dump_stack_lvl+0x57/0x80 check_noncircular+0x119/0x160 ? queued_spin_lock_slowpath+0x4be/0x510 ? __pfx_check_noncircular+0x10/0x10 ? __pfx_queued_spin_lock_slowpath+0x10/0x10 ? mark_lock+0x47/0x160 ? init_chain_block+0x9c/0xc0 ? add_chain_block+0x84/0xf0 check_prev_add+0x195/0x430 __lock_acquire+0xaf0/0xd80 ? __pfx___lock_acquire+0x10/0x10 ? __lock_release.isra.0+0x13b/0x230 lock_acquire.part.0+0x103/0x280 ? filemap_fault+0x26e/0x8b0 ? __pfx_lock_acquire.part.0+0x10/0x10 ? rcu_is_watching+0x34/0x60 ? lock_acquire+0xd7/0x120 down_read+0x95/0x200 ? filemap_fault+0x26e/0x8b0 ? __pfx_down_read+0x10/0x10 ? __filemap_get_folio+0x25/0x1a0 filemap_fault+0x26e/0x8b0 ? __pfx_filemap_fault+0x10/0x10 ? find_held_lock+0x7c/0x90 ? __pfx___lock_release.isra.0+0x10/0x10 ? __pte_offset_map+0x99/0x110 __do_fault+0x57/0xd0 do_pte_missing+0x23b/0x320 __handle_mm_fault+0x2d4/0x320 ? __pfx___handle_mm_fault+0x10/0x10 handle_mm_fault+0x14f/0x260 do_user_addr_fault+0x2a2/0x500 exc_page_fault+0x71/0x90 asm_exc_page_fault+0x22/0x30 Signed-off-by: David Howells <dhowells@redhat.com> Link: https://lore.kernel.org/r/2136178.1721725194@warthog.procyon.org.uk cc: Alexander Viro <viro@zeniv.linux.org.uk> cc: Christian Brauner <brauner@kernel.org> cc: Jan Kara <jack@suse.cz> cc: Jeff Layton <jlayton@kernel.org> cc: Gao Xiang <xiang@kernel.org> cc: Matthew Wilcox <willy@infradead.org> cc: netfs@lists.linux.dev cc: linux-erofs@lists.ozlabs.org cc: linux-fsdevel@vger.kernel.org [brauner: fix minor issues] Signed-off-by: Christian Brauner <brauner@kernel.org>
2024-07-23 09:59:54 +01:00
vfs: Fix potential circular locking through setxattr() and removexattr() When using cachefiles, lockdep may emit something similar to the circular locking dependency notice below. The problem appears to stem from the following: (1) Cachefiles manipulates xattrs on the files in its cache when called from ->writepages(). (2) The setxattr() and removexattr() system call handlers get the name (and value) from userspace after taking the sb_writers lock, putting accesses of the vma->vm_lock and mm->mmap_lock inside of that. (3) The afs filesystem uses a per-inode lock to prevent multiple revalidation RPCs and in writeback vs truncate to prevent parallel operations from deadlocking against the server on one side and local page locks on the other. Fix this by moving the getting of the name and value in {get,remove}xattr() outside of the sb_writers lock. This also has the minor benefits that we don't need to reget these in the event of a retry and we never try to take the sb_writers lock in the event we can't pull the name and value into the kernel. Alternative approaches that might fix this include moving the dispatch of a write to the cache off to a workqueue or trying to do without the validation lock in afs. Note that this might also affect other filesystems that use netfslib and/or cachefiles. ====================================================== WARNING: possible circular locking dependency detected 6.10.0-build2+ #956 Not tainted ------------------------------------------------------ fsstress/6050 is trying to acquire lock: ffff888138fd82f0 (mapping.invalidate_lock#3){++++}-{3:3}, at: filemap_fault+0x26e/0x8b0 but task is already holding lock: ffff888113f26d18 (&vma->vm_lock->lock){++++}-{3:3}, at: lock_vma_under_rcu+0x165/0x250 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #4 (&vma->vm_lock->lock){++++}-{3:3}: __lock_acquire+0xaf0/0xd80 lock_acquire.part.0+0x103/0x280 down_write+0x3b/0x50 vma_start_write+0x6b/0xa0 vma_link+0xcc/0x140 insert_vm_struct+0xb7/0xf0 alloc_bprm+0x2c1/0x390 kernel_execve+0x65/0x1a0 call_usermodehelper_exec_async+0x14d/0x190 ret_from_fork+0x24/0x40 ret_from_fork_asm+0x1a/0x30 -> #3 (&mm->mmap_lock){++++}-{3:3}: __lock_acquire+0xaf0/0xd80 lock_acquire.part.0+0x103/0x280 __might_fault+0x7c/0xb0 strncpy_from_user+0x25/0x160 removexattr+0x7f/0x100 __do_sys_fremovexattr+0x7e/0xb0 do_syscall_64+0x9f/0x100 entry_SYSCALL_64_after_hwframe+0x76/0x7e -> #2 (sb_writers#14){.+.+}-{0:0}: __lock_acquire+0xaf0/0xd80 lock_acquire.part.0+0x103/0x280 percpu_down_read+0x3c/0x90 vfs_iocb_iter_write+0xe9/0x1d0 __cachefiles_write+0x367/0x430 cachefiles_issue_write+0x299/0x2f0 netfs_advance_write+0x117/0x140 netfs_write_folio.isra.0+0x5ca/0x6e0 netfs_writepages+0x230/0x2f0 afs_writepages+0x4d/0x70 do_writepages+0x1e8/0x3e0 filemap_fdatawrite_wbc+0x84/0xa0 __filemap_fdatawrite_range+0xa8/0xf0 file_write_and_wait_range+0x59/0x90 afs_release+0x10f/0x270 __fput+0x25f/0x3d0 __do_sys_close+0x43/0x70 do_syscall_64+0x9f/0x100 entry_SYSCALL_64_after_hwframe+0x76/0x7e -> #1 (&vnode->validate_lock){++++}-{3:3}: __lock_acquire+0xaf0/0xd80 lock_acquire.part.0+0x103/0x280 down_read+0x95/0x200 afs_writepages+0x37/0x70 do_writepages+0x1e8/0x3e0 filemap_fdatawrite_wbc+0x84/0xa0 filemap_invalidate_inode+0x167/0x1e0 netfs_unbuffered_write_iter+0x1bd/0x2d0 vfs_write+0x22e/0x320 ksys_write+0xbc/0x130 do_syscall_64+0x9f/0x100 entry_SYSCALL_64_after_hwframe+0x76/0x7e -> #0 (mapping.invalidate_lock#3){++++}-{3:3}: check_noncircular+0x119/0x160 check_prev_add+0x195/0x430 __lock_acquire+0xaf0/0xd80 lock_acquire.part.0+0x103/0x280 down_read+0x95/0x200 filemap_fault+0x26e/0x8b0 __do_fault+0x57/0xd0 do_pte_missing+0x23b/0x320 __handle_mm_fault+0x2d4/0x320 handle_mm_fault+0x14f/0x260 do_user_addr_fault+0x2a2/0x500 exc_page_fault+0x71/0x90 asm_exc_page_fault+0x22/0x30 other info that might help us debug this: Chain exists of: mapping.invalidate_lock#3 --> &mm->mmap_lock --> &vma->vm_lock->lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- rlock(&vma->vm_lock->lock); lock(&mm->mmap_lock); lock(&vma->vm_lock->lock); rlock(mapping.invalidate_lock#3); *** DEADLOCK *** 1 lock held by fsstress/6050: #0: ffff888113f26d18 (&vma->vm_lock->lock){++++}-{3:3}, at: lock_vma_under_rcu+0x165/0x250 stack backtrace: CPU: 0 PID: 6050 Comm: fsstress Not tainted 6.10.0-build2+ #956 Hardware name: ASUS All Series/H97-PLUS, BIOS 2306 10/09/2014 Call Trace: <TASK> dump_stack_lvl+0x57/0x80 check_noncircular+0x119/0x160 ? queued_spin_lock_slowpath+0x4be/0x510 ? __pfx_check_noncircular+0x10/0x10 ? __pfx_queued_spin_lock_slowpath+0x10/0x10 ? mark_lock+0x47/0x160 ? init_chain_block+0x9c/0xc0 ? add_chain_block+0x84/0xf0 check_prev_add+0x195/0x430 __lock_acquire+0xaf0/0xd80 ? __pfx___lock_acquire+0x10/0x10 ? __lock_release.isra.0+0x13b/0x230 lock_acquire.part.0+0x103/0x280 ? filemap_fault+0x26e/0x8b0 ? __pfx_lock_acquire.part.0+0x10/0x10 ? rcu_is_watching+0x34/0x60 ? lock_acquire+0xd7/0x120 down_read+0x95/0x200 ? filemap_fault+0x26e/0x8b0 ? __pfx_down_read+0x10/0x10 ? __filemap_get_folio+0x25/0x1a0 filemap_fault+0x26e/0x8b0 ? __pfx_filemap_fault+0x10/0x10 ? find_held_lock+0x7c/0x90 ? __pfx___lock_release.isra.0+0x10/0x10 ? __pte_offset_map+0x99/0x110 __do_fault+0x57/0xd0 do_pte_missing+0x23b/0x320 __handle_mm_fault+0x2d4/0x320 ? __pfx___handle_mm_fault+0x10/0x10 handle_mm_fault+0x14f/0x260 do_user_addr_fault+0x2a2/0x500 exc_page_fault+0x71/0x90 asm_exc_page_fault+0x22/0x30 Signed-off-by: David Howells <dhowells@redhat.com> Link: https://lore.kernel.org/r/2136178.1721725194@warthog.procyon.org.uk cc: Alexander Viro <viro@zeniv.linux.org.uk> cc: Christian Brauner <brauner@kernel.org> cc: Jan Kara <jack@suse.cz> cc: Jeff Layton <jlayton@kernel.org> cc: Gao Xiang <xiang@kernel.org> cc: Matthew Wilcox <willy@infradead.org> cc: netfs@lists.linux.dev cc: linux-erofs@lists.ozlabs.org cc: linux-fsdevel@vger.kernel.org [brauner: fix minor issues] Signed-off-by: Christian Brauner <brauner@kernel.org>
2024-07-23 09:59:54 +01:00
vfs: Fix potential circular locking through setxattr() and removexattr() When using cachefiles, lockdep may emit something similar to the circular locking dependency notice below. The problem appears to stem from the following: (1) Cachefiles manipulates xattrs on the files in its cache when called from ->writepages(). (2) The setxattr() and removexattr() system call handlers get the name (and value) from userspace after taking the sb_writers lock, putting accesses of the vma->vm_lock and mm->mmap_lock inside of that. (3) The afs filesystem uses a per-inode lock to prevent multiple revalidation RPCs and in writeback vs truncate to prevent parallel operations from deadlocking against the server on one side and local page locks on the other. Fix this by moving the getting of the name and value in {get,remove}xattr() outside of the sb_writers lock. This also has the minor benefits that we don't need to reget these in the event of a retry and we never try to take the sb_writers lock in the event we can't pull the name and value into the kernel. Alternative approaches that might fix this include moving the dispatch of a write to the cache off to a workqueue or trying to do without the validation lock in afs. Note that this might also affect other filesystems that use netfslib and/or cachefiles. ====================================================== WARNING: possible circular locking dependency detected 6.10.0-build2+ #956 Not tainted ------------------------------------------------------ fsstress/6050 is trying to acquire lock: ffff888138fd82f0 (mapping.invalidate_lock#3){++++}-{3:3}, at: filemap_fault+0x26e/0x8b0 but task is already holding lock: ffff888113f26d18 (&vma->vm_lock->lock){++++}-{3:3}, at: lock_vma_under_rcu+0x165/0x250 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #4 (&vma->vm_lock->lock){++++}-{3:3}: __lock_acquire+0xaf0/0xd80 lock_acquire.part.0+0x103/0x280 down_write+0x3b/0x50 vma_start_write+0x6b/0xa0 vma_link+0xcc/0x140 insert_vm_struct+0xb7/0xf0 alloc_bprm+0x2c1/0x390 kernel_execve+0x65/0x1a0 call_usermodehelper_exec_async+0x14d/0x190 ret_from_fork+0x24/0x40 ret_from_fork_asm+0x1a/0x30 -> #3 (&mm->mmap_lock){++++}-{3:3}: __lock_acquire+0xaf0/0xd80 lock_acquire.part.0+0x103/0x280 __might_fault+0x7c/0xb0 strncpy_from_user+0x25/0x160 removexattr+0x7f/0x100 __do_sys_fremovexattr+0x7e/0xb0 do_syscall_64+0x9f/0x100 entry_SYSCALL_64_after_hwframe+0x76/0x7e -> #2 (sb_writers#14){.+.+}-{0:0}: __lock_acquire+0xaf0/0xd80 lock_acquire.part.0+0x103/0x280 percpu_down_read+0x3c/0x90 vfs_iocb_iter_write+0xe9/0x1d0 __cachefiles_write+0x367/0x430 cachefiles_issue_write+0x299/0x2f0 netfs_advance_write+0x117/0x140 netfs_write_folio.isra.0+0x5ca/0x6e0 netfs_writepages+0x230/0x2f0 afs_writepages+0x4d/0x70 do_writepages+0x1e8/0x3e0 filemap_fdatawrite_wbc+0x84/0xa0 __filemap_fdatawrite_range+0xa8/0xf0 file_write_and_wait_range+0x59/0x90 afs_release+0x10f/0x270 __fput+0x25f/0x3d0 __do_sys_close+0x43/0x70 do_syscall_64+0x9f/0x100 entry_SYSCALL_64_after_hwframe+0x76/0x7e -> #1 (&vnode->validate_lock){++++}-{3:3}: __lock_acquire+0xaf0/0xd80 lock_acquire.part.0+0x103/0x280 down_read+0x95/0x200 afs_writepages+0x37/0x70 do_writepages+0x1e8/0x3e0 filemap_fdatawrite_wbc+0x84/0xa0 filemap_invalidate_inode+0x167/0x1e0 netfs_unbuffered_write_iter+0x1bd/0x2d0 vfs_write+0x22e/0x320 ksys_write+0xbc/0x130 do_syscall_64+0x9f/0x100 entry_SYSCALL_64_after_hwframe+0x76/0x7e -> #0 (mapping.invalidate_lock#3){++++}-{3:3}: check_noncircular+0x119/0x160 check_prev_add+0x195/0x430 __lock_acquire+0xaf0/0xd80 lock_acquire.part.0+0x103/0x280 down_read+0x95/0x200 filemap_fault+0x26e/0x8b0 __do_fault+0x57/0xd0 do_pte_missing+0x23b/0x320 __handle_mm_fault+0x2d4/0x320 handle_mm_fault+0x14f/0x260 do_user_addr_fault+0x2a2/0x500 exc_page_fault+0x71/0x90 asm_exc_page_fault+0x22/0x30 other info that might help us debug this: Chain exists of: mapping.invalidate_lock#3 --> &mm->mmap_lock --> &vma->vm_lock->lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- rlock(&vma->vm_lock->lock); lock(&mm->mmap_lock); lock(&vma->vm_lock->lock); rlock(mapping.invalidate_lock#3); *** DEADLOCK *** 1 lock held by fsstress/6050: #0: ffff888113f26d18 (&vma->vm_lock->lock){++++}-{3:3}, at: lock_vma_under_rcu+0x165/0x250 stack backtrace: CPU: 0 PID: 6050 Comm: fsstress Not tainted 6.10.0-build2+ #956 Hardware name: ASUS All Series/H97-PLUS, BIOS 2306 10/09/2014 Call Trace: <TASK> dump_stack_lvl+0x57/0x80 check_noncircular+0x119/0x160 ? queued_spin_lock_slowpath+0x4be/0x510 ? __pfx_check_noncircular+0x10/0x10 ? __pfx_queued_spin_lock_slowpath+0x10/0x10 ? mark_lock+0x47/0x160 ? init_chain_block+0x9c/0xc0 ? add_chain_block+0x84/0xf0 check_prev_add+0x195/0x430 __lock_acquire+0xaf0/0xd80 ? __pfx___lock_acquire+0x10/0x10 ? __lock_release.isra.0+0x13b/0x230 lock_acquire.part.0+0x103/0x280 ? filemap_fault+0x26e/0x8b0 ? __pfx_lock_acquire.part.0+0x10/0x10 ? rcu_is_watching+0x34/0x60 ? lock_acquire+0xd7/0x120 down_read+0x95/0x200 ? filemap_fault+0x26e/0x8b0 ? __pfx_down_read+0x10/0x10 ? __filemap_get_folio+0x25/0x1a0 filemap_fault+0x26e/0x8b0 ? __pfx_filemap_fault+0x10/0x10 ? find_held_lock+0x7c/0x90 ? __pfx___lock_release.isra.0+0x10/0x10 ? __pte_offset_map+0x99/0x110 __do_fault+0x57/0xd0 do_pte_missing+0x23b/0x320 __handle_mm_fault+0x2d4/0x320 ? __pfx___handle_mm_fault+0x10/0x10 handle_mm_fault+0x14f/0x260 do_user_addr_fault+0x2a2/0x500 exc_page_fault+0x71/0x90 asm_exc_page_fault+0x22/0x30 Signed-off-by: David Howells <dhowells@redhat.com> Link: https://lore.kernel.org/r/2136178.1721725194@warthog.procyon.org.uk cc: Alexander Viro <viro@zeniv.linux.org.uk> cc: Christian Brauner <brauner@kernel.org> cc: Jan Kara <jack@suse.cz> cc: Jeff Layton <jlayton@kernel.org> cc: Gao Xiang <xiang@kernel.org> cc: Matthew Wilcox <willy@infradead.org> cc: netfs@lists.linux.dev cc: linux-erofs@lists.ozlabs.org cc: linux-fsdevel@vger.kernel.org [brauner: fix minor issues] Signed-off-by: Christian Brauner <brauner@kernel.org>
2024-07-23 09:59:54 +01:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
fs/xattr: add *at family syscalls Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc/<pid>/fd/<fd> detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche <cgzones@googlemail.com> Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Christian Brauner <brauner@kernel.org> CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-04-26 18:20:14 +02:00
tmpfs,xattr: enable limited user extended attributes Enable "user." extended attributes on tmpfs, limiting them by tracking the space they occupy, and deducting that space from the limited ispace (unless tmpfs mounted with nr_inodes=0 to leave that ispace unlimited). tmpfs inodes and simple xattrs are both unswappable, and have to be in lowmem on a 32-bit highmem kernel: so the ispace limit is appropriate for xattrs, without any need for a further mount option. Add simple_xattr_space() to give approximate but deterministic estimate of the space taken up by each xattr: with simple_xattrs_free() outputting the space freed if required (but kernfs and even some tmpfs usages do not require that, so don't waste time on strlen'ing if not needed). Security and trusted xattrs were already supported: for consistency and simplicity, account them from the same pool; though there's a small risk that a tmpfs with enough space before would now be considered too small. When extended attributes are used, "df -i" does show more IUsed and less IFree than can be explained by the inodes: document that (manpage later). xfstests tests/generic which were not run on tmpfs before but now pass: 020 037 062 070 077 097 103 117 337 377 454 486 523 533 611 618 728 with no new failures. Signed-off-by: Hugh Dickins <hughd@google.com> Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com> Message-Id: <2e63b26e-df46-5baa-c7d6-f9a8dd3282c5@google.com> Signed-off-by: Christian Brauner <brauner@kernel.org>
2023-08-08 21:33:56 -07:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
fs/xattr.c: fix simple_xattr_list to always include security.* xattrs The vfs has long had a fallback to obtain the security.* xattrs from the LSM when the filesystem does not implement its own listxattr, but shmem/tmpfs and kernfs later gained their own xattr handlers to support other xattrs. Unfortunately, as a side effect, tmpfs and kernfs-based filesystems like sysfs no longer return the synthetic security.* xattr names via listxattr unless they are explicitly set by userspace or initially set upon inode creation after policy load. coreutils has recently switched from unconditionally invoking getxattr for security.* for ls -Z via libselinux to only doing so if listxattr returns the xattr name, breaking ls -Z of such inodes. Before: $ getfattr -m.* /run/initramfs <no output> $ getfattr -m.* /sys/kernel/fscaps <no output> $ setfattr -n user.foo /run/initramfs $ getfattr -m.* /run/initramfs user.foo After: $ getfattr -m.* /run/initramfs security.selinux $ getfattr -m.* /sys/kernel/fscaps security.selinux $ setfattr -n user.foo /run/initramfs $ getfattr -m.* /run/initramfs security.selinux user.foo Link: https://lore.kernel.org/selinux/CAFqZXNtF8wDyQajPCdGn=iOawX4y77ph0EcfcqcUUj+T87FKyA@mail.gmail.com/ Link: https://lore.kernel.org/selinux/20250423175728.3185-2-stephen.smalley.work@gmail.com/ Signed-off-by: Stephen Smalley <stephen.smalley.work@gmail.com> Link: https://lore.kernel.org/20250424152822.2719-1-stephen.smalley.work@gmail.com Fixes: b09e0fa4b4ea66266058ee ("tmpfs: implement generic xattr support") Signed-off-by: Christian Brauner <brauner@kernel.org>
2025-04-24 11:28:20 -04:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
fs/xattr.c: fix simple_xattr_list to always include security.* xattrs The vfs has long had a fallback to obtain the security.* xattrs from the LSM when the filesystem does not implement its own listxattr, but shmem/tmpfs and kernfs later gained their own xattr handlers to support other xattrs. Unfortunately, as a side effect, tmpfs and kernfs-based filesystems like sysfs no longer return the synthetic security.* xattr names via listxattr unless they are explicitly set by userspace or initially set upon inode creation after policy load. coreutils has recently switched from unconditionally invoking getxattr for security.* for ls -Z via libselinux to only doing so if listxattr returns the xattr name, breaking ls -Z of such inodes. Before: $ getfattr -m.* /run/initramfs <no output> $ getfattr -m.* /sys/kernel/fscaps <no output> $ setfattr -n user.foo /run/initramfs $ getfattr -m.* /run/initramfs user.foo After: $ getfattr -m.* /run/initramfs security.selinux $ getfattr -m.* /sys/kernel/fscaps security.selinux $ setfattr -n user.foo /run/initramfs $ getfattr -m.* /run/initramfs security.selinux user.foo Link: https://lore.kernel.org/selinux/CAFqZXNtF8wDyQajPCdGn=iOawX4y77ph0EcfcqcUUj+T87FKyA@mail.gmail.com/ Link: https://lore.kernel.org/selinux/20250423175728.3185-2-stephen.smalley.work@gmail.com/ Signed-off-by: Stephen Smalley <stephen.smalley.work@gmail.com> Link: https://lore.kernel.org/20250424152822.2719-1-stephen.smalley.work@gmail.com Fixes: b09e0fa4b4ea66266058ee ("tmpfs: implement generic xattr support") Signed-off-by: Christian Brauner <brauner@kernel.org>
2025-04-24 11:28:20 -04:00
fs/xattr.c: fix simple_xattr_list to always include security.* xattrs The vfs has long had a fallback to obtain the security.* xattrs from the LSM when the filesystem does not implement its own listxattr, but shmem/tmpfs and kernfs later gained their own xattr handlers to support other xattrs. Unfortunately, as a side effect, tmpfs and kernfs-based filesystems like sysfs no longer return the synthetic security.* xattr names via listxattr unless they are explicitly set by userspace or initially set upon inode creation after policy load. coreutils has recently switched from unconditionally invoking getxattr for security.* for ls -Z via libselinux to only doing so if listxattr returns the xattr name, breaking ls -Z of such inodes. Before: $ getfattr -m.* /run/initramfs <no output> $ getfattr -m.* /sys/kernel/fscaps <no output> $ setfattr -n user.foo /run/initramfs $ getfattr -m.* /run/initramfs user.foo After: $ getfattr -m.* /run/initramfs security.selinux $ getfattr -m.* /sys/kernel/fscaps security.selinux $ setfattr -n user.foo /run/initramfs $ getfattr -m.* /run/initramfs security.selinux user.foo Link: https://lore.kernel.org/selinux/CAFqZXNtF8wDyQajPCdGn=iOawX4y77ph0EcfcqcUUj+T87FKyA@mail.gmail.com/ Link: https://lore.kernel.org/selinux/20250423175728.3185-2-stephen.smalley.work@gmail.com/ Signed-off-by: Stephen Smalley <stephen.smalley.work@gmail.com> Link: https://lore.kernel.org/20250424152822.2719-1-stephen.smalley.work@gmail.com Fixes: b09e0fa4b4ea66266058ee ("tmpfs: implement generic xattr support") Signed-off-by: Christian Brauner <brauner@kernel.org>
2025-04-24 11:28:20 -04:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
bpf: Add simple xattr support to bpffs Add support for extended attributes on bpffs inodes so that user space and BPF LSM programs can attach metadata, for example, a content hash or a security label - to a pinned object or directory. BPF LSM or user space tooling can then uniformly look at this (e.g. security.bpf.*) in similar way to other fs'es. The store is in-memory and non-persistent: it lives only for the lifetime of the mount, like everything else in bpffs. The modelling is similar to tmpfs. bpffs serves the trusted.* and security.* namespaces; user.* is left unsupported. As bpffs is FS_USERNS_MOUNT, security.* is reachable by the unprivileged mounter in a user namespace, and thus we are using the simple_xattr_set_limited infra there (trusted.* needs global CAP_SYS_ADMIN). bpf_fill_super() is open-coded instead of using simple_fill_super(), because the root inode must now be allocated through bpf_fs_alloc_inode() i.e. carry the bpf_fs_inode wrapper and come from the right cache - which requires s_op (and s_xattr) to be installed before the first inode is created. While at it, also harden s_iflags with SB_I_NOEXEC and SB_I_NODEV. bpf_fs_listxattr() is only reachable through the filesystem via i_op->listxattr, so the BPF token inode is left untouched. Name-based fsetxattr()/fgetxattr() on a token fd still work since the get/set handlers are installed at the superblock. For security.* namespace, we use simple_xattr_set_limited() but there was no simple_xattr_add_limited() API yet which was needed in bpf_fs_initxattrs() to avoid underflows in the accounting. The symlink target is freed in bpf_free_inode() rather than in bpf_destroy_inode() so that it is released only after an RCU grace period, as an RCU path walk following the symlink may still dereference inode->i_link in security_inode_follow_link(). Lastly, the bpf_symlink() allocated the symlink target is switched to GFP_KERNEL_ACCOUNT, so the string is charged to the caller's memcg. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://patch.msgid.link/20260602074012.416289-1-daniel@iogearbox.net Cc: Christian Brauner <brauner@kernel.org> Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-02 09:40:12 +02:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
bpf: Add simple xattr support to bpffs Add support for extended attributes on bpffs inodes so that user space and BPF LSM programs can attach metadata, for example, a content hash or a security label - to a pinned object or directory. BPF LSM or user space tooling can then uniformly look at this (e.g. security.bpf.*) in similar way to other fs'es. The store is in-memory and non-persistent: it lives only for the lifetime of the mount, like everything else in bpffs. The modelling is similar to tmpfs. bpffs serves the trusted.* and security.* namespaces; user.* is left unsupported. As bpffs is FS_USERNS_MOUNT, security.* is reachable by the unprivileged mounter in a user namespace, and thus we are using the simple_xattr_set_limited infra there (trusted.* needs global CAP_SYS_ADMIN). bpf_fill_super() is open-coded instead of using simple_fill_super(), because the root inode must now be allocated through bpf_fs_alloc_inode() i.e. carry the bpf_fs_inode wrapper and come from the right cache - which requires s_op (and s_xattr) to be installed before the first inode is created. While at it, also harden s_iflags with SB_I_NOEXEC and SB_I_NODEV. bpf_fs_listxattr() is only reachable through the filesystem via i_op->listxattr, so the BPF token inode is left untouched. Name-based fsetxattr()/fgetxattr() on a token fd still work since the get/set handlers are installed at the superblock. For security.* namespace, we use simple_xattr_set_limited() but there was no simple_xattr_add_limited() API yet which was needed in bpf_fs_initxattrs() to avoid underflows in the accounting. The symlink target is freed in bpf_free_inode() rather than in bpf_destroy_inode() so that it is released only after an RCU grace period, as an RCU path walk following the symlink may still dereference inode->i_link in security_inode_follow_link(). Lastly, the bpf_symlink() allocated the symlink target is switched to GFP_KERNEL_ACCOUNT, so the string is charged to the caller's memcg. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://patch.msgid.link/20260602074012.416289-1-daniel@iogearbox.net Cc: Christian Brauner <brauner@kernel.org> Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-02 09:40:12 +02:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
bpf: Add simple xattr support to bpffs Add support for extended attributes on bpffs inodes so that user space and BPF LSM programs can attach metadata, for example, a content hash or a security label - to a pinned object or directory. BPF LSM or user space tooling can then uniformly look at this (e.g. security.bpf.*) in similar way to other fs'es. The store is in-memory and non-persistent: it lives only for the lifetime of the mount, like everything else in bpffs. The modelling is similar to tmpfs. bpffs serves the trusted.* and security.* namespaces; user.* is left unsupported. As bpffs is FS_USERNS_MOUNT, security.* is reachable by the unprivileged mounter in a user namespace, and thus we are using the simple_xattr_set_limited infra there (trusted.* needs global CAP_SYS_ADMIN). bpf_fill_super() is open-coded instead of using simple_fill_super(), because the root inode must now be allocated through bpf_fs_alloc_inode() i.e. carry the bpf_fs_inode wrapper and come from the right cache - which requires s_op (and s_xattr) to be installed before the first inode is created. While at it, also harden s_iflags with SB_I_NOEXEC and SB_I_NODEV. bpf_fs_listxattr() is only reachable through the filesystem via i_op->listxattr, so the BPF token inode is left untouched. Name-based fsetxattr()/fgetxattr() on a token fd still work since the get/set handlers are installed at the superblock. For security.* namespace, we use simple_xattr_set_limited() but there was no simple_xattr_add_limited() API yet which was needed in bpf_fs_initxattrs() to avoid underflows in the accounting. The symlink target is freed in bpf_free_inode() rather than in bpf_destroy_inode() so that it is released only after an RCU grace period, as an RCU path walk following the symlink may still dereference inode->i_link in security_inode_follow_link(). Lastly, the bpf_symlink() allocated the symlink target is switched to GFP_KERNEL_ACCOUNT, so the string is charged to the caller's memcg. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://patch.msgid.link/20260602074012.416289-1-daniel@iogearbox.net Cc: Christian Brauner <brauner@kernel.org> Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-02 09:40:12 +02:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
bpf: Add simple xattr support to bpffs Add support for extended attributes on bpffs inodes so that user space and BPF LSM programs can attach metadata, for example, a content hash or a security label - to a pinned object or directory. BPF LSM or user space tooling can then uniformly look at this (e.g. security.bpf.*) in similar way to other fs'es. The store is in-memory and non-persistent: it lives only for the lifetime of the mount, like everything else in bpffs. The modelling is similar to tmpfs. bpffs serves the trusted.* and security.* namespaces; user.* is left unsupported. As bpffs is FS_USERNS_MOUNT, security.* is reachable by the unprivileged mounter in a user namespace, and thus we are using the simple_xattr_set_limited infra there (trusted.* needs global CAP_SYS_ADMIN). bpf_fill_super() is open-coded instead of using simple_fill_super(), because the root inode must now be allocated through bpf_fs_alloc_inode() i.e. carry the bpf_fs_inode wrapper and come from the right cache - which requires s_op (and s_xattr) to be installed before the first inode is created. While at it, also harden s_iflags with SB_I_NOEXEC and SB_I_NODEV. bpf_fs_listxattr() is only reachable through the filesystem via i_op->listxattr, so the BPF token inode is left untouched. Name-based fsetxattr()/fgetxattr() on a token fd still work since the get/set handlers are installed at the superblock. For security.* namespace, we use simple_xattr_set_limited() but there was no simple_xattr_add_limited() API yet which was needed in bpf_fs_initxattrs() to avoid underflows in the accounting. The symlink target is freed in bpf_free_inode() rather than in bpf_destroy_inode() so that it is released only after an RCU grace period, as an RCU path walk following the symlink may still dereference inode->i_link in security_inode_follow_link(). Lastly, the bpf_symlink() allocated the symlink target is switched to GFP_KERNEL_ACCOUNT, so the string is charged to the caller's memcg. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://patch.msgid.link/20260602074012.416289-1-daniel@iogearbox.net Cc: Christian Brauner <brauner@kernel.org> Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-02 09:40:12 +02:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
bpf: Add simple xattr support to bpffs Add support for extended attributes on bpffs inodes so that user space and BPF LSM programs can attach metadata, for example, a content hash or a security label - to a pinned object or directory. BPF LSM or user space tooling can then uniformly look at this (e.g. security.bpf.*) in similar way to other fs'es. The store is in-memory and non-persistent: it lives only for the lifetime of the mount, like everything else in bpffs. The modelling is similar to tmpfs. bpffs serves the trusted.* and security.* namespaces; user.* is left unsupported. As bpffs is FS_USERNS_MOUNT, security.* is reachable by the unprivileged mounter in a user namespace, and thus we are using the simple_xattr_set_limited infra there (trusted.* needs global CAP_SYS_ADMIN). bpf_fill_super() is open-coded instead of using simple_fill_super(), because the root inode must now be allocated through bpf_fs_alloc_inode() i.e. carry the bpf_fs_inode wrapper and come from the right cache - which requires s_op (and s_xattr) to be installed before the first inode is created. While at it, also harden s_iflags with SB_I_NOEXEC and SB_I_NODEV. bpf_fs_listxattr() is only reachable through the filesystem via i_op->listxattr, so the BPF token inode is left untouched. Name-based fsetxattr()/fgetxattr() on a token fd still work since the get/set handlers are installed at the superblock. For security.* namespace, we use simple_xattr_set_limited() but there was no simple_xattr_add_limited() API yet which was needed in bpf_fs_initxattrs() to avoid underflows in the accounting. The symlink target is freed in bpf_free_inode() rather than in bpf_destroy_inode() so that it is released only after an RCU grace period, as an RCU path walk following the symlink may still dereference inode->i_link in security_inode_follow_link(). Lastly, the bpf_symlink() allocated the symlink target is switched to GFP_KERNEL_ACCOUNT, so the string is charged to the caller's memcg. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://patch.msgid.link/20260602074012.416289-1-daniel@iogearbox.net Cc: Christian Brauner <brauner@kernel.org> Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-02 09:40:12 +02:00
bpf: Add simple xattr support to bpffs Add support for extended attributes on bpffs inodes so that user space and BPF LSM programs can attach metadata, for example, a content hash or a security label - to a pinned object or directory. BPF LSM or user space tooling can then uniformly look at this (e.g. security.bpf.*) in similar way to other fs'es. The store is in-memory and non-persistent: it lives only for the lifetime of the mount, like everything else in bpffs. The modelling is similar to tmpfs. bpffs serves the trusted.* and security.* namespaces; user.* is left unsupported. As bpffs is FS_USERNS_MOUNT, security.* is reachable by the unprivileged mounter in a user namespace, and thus we are using the simple_xattr_set_limited infra there (trusted.* needs global CAP_SYS_ADMIN). bpf_fill_super() is open-coded instead of using simple_fill_super(), because the root inode must now be allocated through bpf_fs_alloc_inode() i.e. carry the bpf_fs_inode wrapper and come from the right cache - which requires s_op (and s_xattr) to be installed before the first inode is created. While at it, also harden s_iflags with SB_I_NOEXEC and SB_I_NODEV. bpf_fs_listxattr() is only reachable through the filesystem via i_op->listxattr, so the BPF token inode is left untouched. Name-based fsetxattr()/fgetxattr() on a token fd still work since the get/set handlers are installed at the superblock. For security.* namespace, we use simple_xattr_set_limited() but there was no simple_xattr_add_limited() API yet which was needed in bpf_fs_initxattrs() to avoid underflows in the accounting. The symlink target is freed in bpf_free_inode() rather than in bpf_destroy_inode() so that it is released only after an RCU grace period, as an RCU path walk following the symlink may still dereference inode->i_link in security_inode_follow_link(). Lastly, the bpf_symlink() allocated the symlink target is switched to GFP_KERNEL_ACCOUNT, so the string is charged to the caller's memcg. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://patch.msgid.link/20260602074012.416289-1-daniel@iogearbox.net Cc: Christian Brauner <brauner@kernel.org> Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-02 09:40:12 +02:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
tmpfs,xattr: enable limited user extended attributes Enable "user." extended attributes on tmpfs, limiting them by tracking the space they occupy, and deducting that space from the limited ispace (unless tmpfs mounted with nr_inodes=0 to leave that ispace unlimited). tmpfs inodes and simple xattrs are both unswappable, and have to be in lowmem on a 32-bit highmem kernel: so the ispace limit is appropriate for xattrs, without any need for a further mount option. Add simple_xattr_space() to give approximate but deterministic estimate of the space taken up by each xattr: with simple_xattrs_free() outputting the space freed if required (but kernfs and even some tmpfs usages do not require that, so don't waste time on strlen'ing if not needed). Security and trusted xattrs were already supported: for consistency and simplicity, account them from the same pool; though there's a small risk that a tmpfs with enough space before would now be considered too small. When extended attributes are used, "df -i" does show more IUsed and less IFree than can be explained by the inodes: document that (manpage later). xfstests tests/generic which were not run on tmpfs before but now pass: 020 037 062 070 077 097 103 117 337 377 454 486 523 533 611 618 728 with no new failures. Signed-off-by: Hugh Dickins <hughd@google.com> Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com> Message-Id: <2e63b26e-df46-5baa-c7d6-f9a8dd3282c5@google.com> Signed-off-by: Christian Brauner <brauner@kernel.org>
2023-08-08 21:33:56 -07:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00
xattr: use rbtree for simple_xattrs A while ago Vasily reported that it is possible to set a large number of xattrs on inodes of filesystems that make use of the simple xattr infrastructure. This includes all kernfs-based filesystems that support xattrs (e.g., cgroupfs and tmpfs). Both cgroupfs and tmpfs can be mounted by unprivileged users in unprivileged containers and root in an unprivileged container can set an unrestricted number of security.* xattrs and privileged users can also set unlimited trusted.* xattrs. As there are apparently users that have a fairly large number of xattrs we should scale a bit better. Other xattrs such as user.* are restricted for kernfs-based instances to a fairly limited number. Using a simple linked list protected by a spinlock used for set, get, and list operations doesn't scale well if users use a lot of xattrs even if it's not a crazy number. There's no need to bring in the big guns like rhashtables or rw semaphores for this. An rbtree with a rwlock, or limited rcu semanics and seqlock is enough. It scales within the constraints we are working in. By far the most common operation is getting an xattr. Setting xattrs should be a moderately rare operation. And listxattr() often only happens when copying xattrs between files or together with the contents to a new file. Holding a lock across listxattr() is unproblematic because it doesn't list the values of xattrs. It can only be used to list the names of all xattrs set on a file. And the number of xattr names that can be listed with listxattr() is limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names are found it will return -E2BIG. In short, the maximum amount of memory that can be retrieved via listxattr() is limited. Of course, the API is broken as documented on xattr(7) already. In the future we might want to address this but for now this is the world we live in and have lived for a long time. But it does indeed mean that once an application goes over XATTR_LIST_MAX limit of xattrs set on an inode it isn't possible to copy the file and include its xattrs in the copy unless the caller knows all xattrs or limits the copy of the xattrs to important ones it knows by name (At least for tmpfs, and kernfs-based filesystems. Other filesystems might provide ways of achieving this.). Bonus of this port to rbtree+rwlock is that we shrink the memory consumption for users of the simple xattr infrastructure. Also add proper kernel documentation to all the functions. A big thanks to Paul for his comments. Cc: Vasily Averin <vvs@openvz.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-11-04 13:52:42 +01:00
tmpfs,xattr: enable limited user extended attributes Enable "user." extended attributes on tmpfs, limiting them by tracking the space they occupy, and deducting that space from the limited ispace (unless tmpfs mounted with nr_inodes=0 to leave that ispace unlimited). tmpfs inodes and simple xattrs are both unswappable, and have to be in lowmem on a 32-bit highmem kernel: so the ispace limit is appropriate for xattrs, without any need for a further mount option. Add simple_xattr_space() to give approximate but deterministic estimate of the space taken up by each xattr: with simple_xattrs_free() outputting the space freed if required (but kernfs and even some tmpfs usages do not require that, so don't waste time on strlen'ing if not needed). Security and trusted xattrs were already supported: for consistency and simplicity, account them from the same pool; though there's a small risk that a tmpfs with enough space before would now be considered too small. When extended attributes are used, "df -i" does show more IUsed and less IFree than can be explained by the inodes: document that (manpage later). xfstests tests/generic which were not run on tmpfs before but now pass: 020 037 062 070 077 097 103 117 337 377 454 486 523 533 611 618 728 with no new failures. Signed-off-by: Hugh Dickins <hughd@google.com> Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com> Message-Id: <2e63b26e-df46-5baa-c7d6-f9a8dd3282c5@google.com> Signed-off-by: Christian Brauner <brauner@kernel.org>
2023-08-08 21:33:56 -07:00
simpe_xattr: use per-sb cache Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-06-05 15:53:19 +02:00