The current code to override credentials for creation operations is
pretty difficult to understand. We effectively override the credentials
twice:
(1) override with the mounter's credentials
(2) copy the mounts credentials and override the fs{g,u}id with the inode {u,g}id
And then we elide the revert because it would be an idempotent revert.
That elision doesn't buy us anything anymore though because I've made it
all work without any reference counting anyway. All it does is mix the
two credential overrides together.
We can use a cleanup guard to clarify the creation codepaths and make
them easier to understand.
This just introduces the cleanup guard keeping the patch reviewable.
We'll convert the caller in follow-up patches and then drop the
duplicated code.
Link: https://patch.msgid.link/20251117-work-ovl-cred-guard-prepare-v2-1-bd1c97a36d7b@kernel.org
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Christian Brauner <brauner@kernel.org> says:
This adds an overlayfs specific extension of the cred guard
infrastructure I introduced. This allows all of overlayfs to be ported
to cred guards. I refactored a few functions to reduce the scope of the
cred guard. I think this is beneficial as it's visually very easy to
grasp the scope in one go. Lightly tested.
* patches from https://patch.msgid.link/20251117-work-ovl-cred-guard-v4-0-b31603935724@kernel.org: (42 commits)
ovl: remove ovl_revert_creds()
ovl: port ovl_fill_super() to cred guard
ovl: refactor ovl_fill_super()
ovl: port ovl_lower_positive() to cred guard
ovl: port ovl_lookup() to cred guard
ovl: refactor ovl_lookup()
ovl: port ovl_copyfile() to cred guard
ovl: port ovl_rename() to cred guard
ovl: refactor ovl_rename()
ovl: introduce struct ovl_renamedata
ovl: port ovl_listxattr() to cred guard
ovl: port ovl_xattr_get() to cred guard
ovl: port ovl_xattr_set() to cred guard
ovl: port ovl_nlink_end() to cred guard
ovl: port ovl_nlink_start() to cred guard
ovl: port ovl_check_empty_dir() to cred guard
ovl: port ovl_dir_llseek() to cred guard
ovl: refactor ovl_iterate() and port to cred guard
ovl: don't override credentials for ovl_check_whiteouts()
ovl: port ovl_maybe_lookup_lowerdata() to cred guard
...
Link: https://patch.msgid.link/20251117-work-ovl-cred-guard-v4-0-b31603935724@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
Extract the code that runs under overridden credentials into a separate
ovl_rename_upper() helper function and the code that runs before/after to
ovl_rename_start/end(). Error handling is simplified.
The helpers returns errors directly instead of using goto labels.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Link: https://patch.msgid.link/20251117-work-ovl-cred-guard-v4-34-b31603935724@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
Add a struct ovl_renamedata to group rename-related state that was
previously stored in local variables. Embedd struct renamedata directly
aligning with the vfs.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Link: https://patch.msgid.link/20251117-work-ovl-cred-guard-v4-33-b31603935724@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
Overlayfs plucks the relevant creds from the superblock. Extend the
override_creds cleanup class I added to override_creds_ovl which uses
the ovl_override_creds() function as initialization helper. Add
with_ovl_creds() based on this new class.
Link: https://patch.msgid.link/20251117-work-ovl-cred-guard-v4-1-b31603935724@kernel.org
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Bring in the directory locking changes as they touch overlayfs in a
pretty substantial way and we are about to change the credential
override semantics quite substantially as well.
Signed-off-by: Christian Brauner <brauner@kernel.org>
Bring in the shared branch with the kbuild tree to enable
'-fms-extensions' for 6.19. The overlayfs cred guard work
depends on this.
Signed-off-by: Christian Brauner <brauner@kernel.org>
NeilBrown <neilb@ownmail.net> says:
This series is the next part of my effort to change directory-op
locking to allow multiple concurrent ops in a directory. Ultimately we
will (in my plan) lock the target dentry(s) rather than the whole
parent directory.
To help with changing the locking protocol, this series centralises
locking and lookup in some helpers. The various helpers are introduced
and then used in the same patch - roughly one patch per helper though
with various exceptions.
I haven't introduced these helpers into the various filesystems that
Al's tree-in-dcache series is changing. That series introduces and
uses similar helpers tuned to the specific needs of that set of
filesystems. Ultimately all the helpers will use the same backends
which can then be adjusted when it is time to change the locking
protocol.
One change that deserves highlighting is in patch 13 where vfs_mkdir()
is changed to unlock the parent on failure, as well as the current
behaviour of dput()ing the dentry on failure. Once this change is in
place, the final step of both create and an remove sequences only
requires the target dentry, not the parent. So e.g. end_creating() is
only given the dentry (which may be IS_ERR() after vfs_mkdir()). This
helps establish the pattern that it is the dentry that is being locked
and unlocked (the lock is currently held on dentry->d_parent->d_inode,
but that can change).
* patches from https://patch.msgid.link/20251113002050.676694-1-neilb@ownmail.net:
VFS: introduce end_creating_keep()
VFS: change vfs_mkdir() to unlock on failure.
ecryptfs: use new start_creating/start_removing APIs
Add start_renaming_two_dentries()
VFS/ovl/smb: introduce start_renaming_dentry()
VFS/nfsd/ovl: introduce start_renaming() and end_renaming()
VFS: add start_creating_killable() and start_removing_killable()
VFS: introduce start_removing_dentry()
smb/server: use end_removing_noperm for for target of smb2_create_link()
VFS: introduce start_creating_noperm() and start_removing_noperm()
VFS/nfsd/cachefiles/ovl: introduce start_removing() and end_removing()
VFS/nfsd/cachefiles/ovl: add start_creating() and end_creating()
VFS: tidy up do_unlinkat()
VFS: introduce start_dirop() and end_dirop()
debugfs: rename end_creating() to debugfs_end_creating()
Link: https://patch.msgid.link/20251113002050.676694-1-neilb@ownmail.net
Signed-off-by: Christian Brauner <brauner@kernel.org>
Occasionally the caller of end_creating() wants to keep using the dentry.
Rather then requiring them to dget() the dentry (when not an error)
before calling end_creating(), provide end_creating_keep() which does
this.
cachefiles and overlayfs make use of this.
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
Link: https://patch.msgid.link/20251113002050.676694-16-neilb@ownmail.net
Tested-by: syzbot@syzkaller.appspotmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
