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linux/fs/xfs
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Kees Cook d3b428f036 fs: create and use seq_show_option for escaping 
commit a068acf2ee upstream.

Many file systems that implement the show_options hook fail to correctly
escape their output which could lead to unescaped characters (e.g.  new
lines) leaking into /proc/mounts and /proc/[pid]/mountinfo files.  This
could lead to confusion, spoofed entries (resulting in things like
systemd issuing false d-bus "mount" notifications), and who knows what
else.  This looks like it would only be the root user stepping on
themselves, but it's possible weird things could happen in containers or
in other situations with delegated mount privileges.

Here's an example using overlay with setuid fusermount trusting the
contents of /proc/mounts (via the /etc/mtab symlink).  Imagine the use
of "sudo" is something more sneaky:

  $ BASE="ovl"
  $ MNT="$BASE/mnt"
  $ LOW="$BASE/lower"
  $ UP="$BASE/upper"
  $ WORK="$BASE/work/ 0 0
  none /proc fuse.pwn user_id=1000"
  $ mkdir -p "$LOW" "$UP" "$WORK"
  $ sudo mount -t overlay -o "lowerdir=$LOW,upperdir=$UP,workdir=$WORK" none /mnt
  $ cat /proc/mounts
  none /root/ovl/mnt overlay rw,relatime,lowerdir=ovl/lower,upperdir=ovl/upper,workdir=ovl/work/ 0 0
  none /proc fuse.pwn user_id=1000 0 0
  $ fusermount -u /proc
  $ cat /proc/mounts
  cat: /proc/mounts: No such file or directory

This fixes the problem by adding new seq_show_option and
seq_show_option_n helpers, and updating the vulnerable show_option
handlers to use them as needed.  Some, like SELinux, need to be open
coded due to unusual existing escape mechanisms.

[akpm@linux-foundation.org: add lost chunk, per Kees]
[keescook@chromium.org: seq_show_option should be using const parameters]
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Acked-by: Jan Kara <jack@suse.com>
Acked-by: Paul Moore <paul@paul-moore.com>
Cc: J. R. Okajima <hooanon05g@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2015-09-21 10:05:45 -07:00
..
libxfs xfs: Fix file type directory corruption for btree directories 2015-09-21 10:05:37 -07:00
Kconfig xfs: require 64-bit sector_t 2014-07-30 09:12:05 +10:00
kmem.c xfs: change kmem_free to use generic kvfree() 2015-02-02 09:54:18 +11:00
kmem.h xfs: change kmem_free to use generic kvfree() 2015-02-02 09:54:18 +11:00
Makefile xfs: implement pNFS export operations 2015-02-16 11:49:23 +11:00
mrlock.h xfs: introduce CONFIG_XFS_WARN 2013-05-07 18:45:36 -05:00
uuid.c xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
uuid.h xfs: add CRC infrastructure 2012-11-19 20:11:24 -06:00
xfs.h xfs: introduce CONFIG_XFS_WARN 2013-05-07 18:45:36 -05:00
xfs_acl.c xfs: move most of xfs_sb.h to xfs_format.h 2014-11-28 14:27:09 +11:00
xfs_acl.h xfs: move acl structures to xfs_format.h 2014-11-28 14:24:37 +11:00
xfs_aops.c xfs: update for 4.1-rc1 2015-04-24 07:08:41 -07:00
xfs_aops.h xfs: don't allocate an ioend for direct I/O completions 2015-02-02 10:02:09 +11:00
xfs_attr.h xfs: kill xfs_vnodeops.[ch] 2013-08-12 16:53:39 -05:00
xfs_attr_inactive.c xfs: don't truncate attribute extents if no extents exist 2015-08-03 09:29:11 -07:00
xfs_attr_list.c xfs: pass attr geometry to attr leaf header conversion functions 2015-04-13 11:26:02 +10:00
xfs_bit.c xfs: fix static and extern sparse warnings 2013-10-30 13:59:56 -05:00
xfs_bmap_util.c Merge branch 'xfs-misc-fixes-for-4.1-3' into for-next 2015-04-13 11:40:16 +10:00
xfs_bmap_util.h xfs: Add support FALLOC_FL_INSERT_RANGE for fallocate 2015-03-25 15:08:56 +11:00
xfs_buf.c list_lru: add helpers to isolate items 2015-02-12 18:54:10 -08:00
xfs_buf.h xfs: split metadata and log buffer completion to separate workqueues 2014-12-04 09:43:17 +11:00
xfs_buf_item.c xfs: clarify async write failure ratelimit message 2015-02-24 10:14:04 +11:00
xfs_buf_item.h xfs: decouple inode and bmap btree header files 2013-10-23 16:28:49 -05:00
xfs_dir2_readdir.c Merge branch 'xfs-misc-fixes-for-3.19-2' into for-next 2014-12-04 09:46:17 +11:00
xfs_discard.c xfs: pass mp to XFS_WANT_CORRUPTED_GOTO 2015-02-23 22:39:08 +11:00
xfs_discard.h xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_dquot.c xfs: move most of xfs_sb.h to xfs_format.h 2014-11-28 14:27:09 +11:00
xfs_dquot.h xfs: fix implicit bool to int conversion 2015-01-09 10:48:58 +11:00
xfs_dquot_item.c xfs: move most of xfs_sb.h to xfs_format.h 2014-11-28 14:27:09 +11:00
xfs_dquot_item.h xfs: remove the quotaoff log format from the quotaoff log item 2013-12-13 11:34:08 +11:00
xfs_error.c xfs: %pF is only for function pointers 2015-03-25 14:56:21 +11:00
xfs_error.h xfs: pass mp to XFS_WANT_CORRUPTED_RETURN 2015-02-23 22:39:13 +11:00
xfs_export.c VFS: normal filesystems (and lustre): d_inode() annotations 2015-04-15 15:06:57 -04:00
xfs_export.h xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_extent_busy.c xfs: merge xfs_ag.h into xfs_format.h 2014-11-28 14:25:04 +11:00
xfs_extent_busy.h xfs: decouple inode and bmap btree header files 2013-10-23 16:28:49 -05:00
xfs_extfree_item.c xfs: move most of xfs_sb.h to xfs_format.h 2014-11-28 14:27:09 +11:00
xfs_extfree_item.h xfs: split out EFI/EFD log item format definition 2013-08-12 16:07:13 -05:00
xfs_file.c xfs: xfs_iozero can return positive errno 2015-05-29 07:40:32 +10:00
xfs_filestream.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-04-26 17:22:07 -07:00
xfs_filestream.h xfs: add filestream allocator tracepoints 2014-04-23 07:11:52 +10:00
xfs_fsops.c xfs: remove xfs_mod_incore_sb API 2015-02-23 21:24:37 +11:00
xfs_fsops.h xfs: ensure log covering transactions are synchronous 2011-01-11 20:28:17 -06:00
xfs_globals.c xfs: export log_recovery_delay to delay mount time log recovery 2014-09-09 11:56:13 +10:00
xfs_icache.c xfs: inodes are new until the dentry cache is set up 2015-02-23 22:38:08 +11:00
xfs_icache.h xfs: merge xfs_ag.h into xfs_format.h 2014-11-28 14:25:04 +11:00
xfs_icreate_item.c xfs: move most of xfs_sb.h to xfs_format.h 2014-11-28 14:27:09 +11:00
xfs_icreate_item.h xfs: separate icreate log format definitions from xfs_icreate_item.h 2013-08-12 16:10:35 -05:00
xfs_inode.c xfs: fix broken i_nlink accounting for whiteout tmpfile inode 2015-05-29 08:14:55 +10:00
xfs_inode.h Merge branch 'xfs-mmap-lock' into for-next 2015-02-24 10:27:47 +11:00
xfs_inode_item.c xfs: move most of xfs_sb.h to xfs_format.h 2014-11-28 14:27:09 +11:00
xfs_inode_item.h xfs: remove the inode log format from the inode log item 2013-12-13 11:34:05 +11:00
xfs_ioctl.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-04-26 17:22:07 -07:00
xfs_ioctl.h xfs: consolidate extent swap code 2013-08-12 16:56:06 -05:00
xfs_ioctl32.c VFS: normal filesystems (and lustre): d_inode() annotations 2015-04-15 15:06:57 -04:00
xfs_ioctl32.h xfs: compat_xfs_bstat does not have forkoff 2014-10-02 09:17:58 +10:00
xfs_iomap.c xfs: Remove icsb infrastructure 2015-02-23 21:22:31 +11:00
xfs_iomap.h xfs: pass a 64-bit count argument to xfs_iomap_write_unwritten 2015-01-09 10:48:12 +11:00
xfs_iops.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-04-26 17:22:07 -07:00
xfs_iops.h xfs: inodes are new until the dentry cache is set up 2015-02-23 22:38:08 +11:00
xfs_itable.c xfs: pass mp to XFS_WANT_CORRUPTED_RETURN 2015-02-23 22:39:13 +11:00
xfs_itable.h xfs: bulkstat chunk formatting cursor is broken 2014-11-07 08:30:30 +11:00
xfs_linux.h xfs: Remove icsb infrastructure 2015-02-23 21:22:31 +11:00
xfs_log.c Merge branch 'xfs-sb-logging-rework' into for-next 2015-01-22 09:20:53 +11:00
xfs_log.h xfs: log vector rounding leaks log space 2014-05-20 08:18:09 +10:00
xfs_log_cil.c xfs: move most of xfs_sb.h to xfs_format.h 2014-11-28 14:27:09 +11:00
xfs_log_priv.h xfs: add xlog sysfs kobject and attribute handlers 2014-07-15 08:07:29 +10:00
xfs_log_recover.c xfs: remote attribute headers contain an invalid LSN 2015-08-10 12:21:59 -07:00
xfs_message.c xfs: move most of xfs_sb.h to xfs_format.h 2014-11-28 14:27:09 +11:00
xfs_message.h xfs: introduce CONFIG_XFS_WARN 2013-05-07 18:45:36 -05:00
xfs_mount.c xfs: inode and free block counters need to use __percpu_counter_compare 2015-05-29 07:39:34 +10:00
xfs_mount.h xfs: remove xfs_mod_incore_sb API 2015-02-23 21:24:37 +11:00
xfs_mru_cache.c xfs: xfs_mru_cache_insert() should use GFP_NOFS 2015-03-25 14:57:53 +11:00
xfs_mru_cache.h xfs: embedd mru_elem into parent structure 2014-04-23 07:11:51 +10:00
xfs_pnfs.c Merge branch 'xfs-misc-fixes-for-4.1-3' into for-next 2015-04-13 11:40:16 +10:00
xfs_pnfs.h xfs: unlock i_mutex in xfs_break_layouts 2015-04-13 11:38:29 +10:00
xfs_qm.c Merge branch 'xfs-misc-fixes-for-4.1' into for-next 2015-02-24 10:24:07 +11:00
xfs_qm.h xfs: Convert to using ->get_state callback 2015-03-04 16:06:36 +01:00
xfs_qm_bhv.c xfs: move most of xfs_sb.h to xfs_format.h 2014-11-28 14:27:09 +11:00
xfs_qm_syscalls.c xfs: Convert to using ->get_state callback 2015-03-04 16:06:36 +01:00
xfs_quota.h xfs: split dquot buffer operations out 2013-10-23 14:28:35 -05:00
xfs_quotaops.c xfs: Add support for Q_SETINFO 2015-03-04 16:06:38 +01:00
xfs_rtalloc.c xfs: move most of xfs_sb.h to xfs_format.h 2014-11-28 14:27:09 +11:00
xfs_rtalloc.h xfs: combine xfs_rtmodify_summary and xfs_rtget_summary 2014-09-09 11:58:42 +10:00
xfs_stats.c xfs: support the XFS_BTNUM_FINOBT free inode btree type 2014-04-24 16:00:52 +10:00
xfs_stats.h xfs: support the XFS_BTNUM_FINOBT free inode btree type 2014-04-24 16:00:52 +10:00
xfs_super.c fs: create and use seq_show_option for escaping 2015-09-21 10:05:45 -07:00
xfs_super.h xfs: Remove icsb infrastructure 2015-02-23 21:22:31 +11:00
xfs_symlink.c xfs: fix remote symlinks on V5/CRC filesystems 2015-08-03 09:29:11 -07:00
xfs_symlink.h xfs: push down inactive transaction mgmt for remote symlinks 2013-10-08 14:53:02 -05:00
xfs_sysctl.c xfs: remove deprecated sysctls 2015-01-09 10:47:43 +11:00
xfs_sysctl.h xfs: export log_recovery_delay to delay mount time log recovery 2014-09-09 11:56:13 +10:00
xfs_sysfs.c xfs: export log_recovery_delay to delay mount time log recovery 2014-09-09 11:56:13 +10:00
xfs_sysfs.h xfs: add debug sysfs attribute set 2014-09-09 11:52:42 +10:00
xfs_trace.c xfs: move most of xfs_sb.h to xfs_format.h 2014-11-28 14:27:09 +11:00
xfs_trace.h Merge branch 'xfs-dio-extend-fix' into for-next 2015-04-16 22:13:18 +10:00
xfs_trans.c xfs: replace xfs_mod_incore_sb_batched 2015-02-23 21:24:11 +11:00
xfs_trans.h xfs: format log items write directly into the linear CIL buffer 2013-12-13 11:34:02 +11:00
xfs_trans_ail.c xfs: move most of xfs_sb.h to xfs_format.h 2014-11-28 14:27:09 +11:00
xfs_trans_buf.c xfs: only trace buffer items if they exist 2015-02-10 09:23:40 +11:00
xfs_trans_dquot.c xfs: move most of xfs_sb.h to xfs_format.h 2014-11-28 14:27:09 +11:00
xfs_trans_extfree.c xfs: move most of xfs_sb.h to xfs_format.h 2014-11-28 14:27:09 +11:00
xfs_trans_inode.c xfs: move most of xfs_sb.h to xfs_format.h 2014-11-28 14:27:09 +11:00
xfs_trans_priv.h xfs: remove unused ail pointer arg from xfs_trans_ail_cursor_done() 2014-04-14 19:06:05 +10:00
xfs_xattr.c VFS: normal filesystems (and lustre): d_inode() annotations 2015-04-15 15:06:57 -04:00