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Kees Cook a068acf2ee fs: create and use seq_show_option for escaping 
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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 		2015-09-04 16:54:41 -07:00
..
libxfs xfs: remote attributes need to be considered data 2015-07-29 11:48:02 +10:00
Kconfig xfs: require 64-bit sector_t 2014-07-30 09:12:05 +10:00
Makefile xfs: implement pNFS export operations 2015-02-16 11:49:23 +11:00
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
mrlock.h xfs: introduce CONFIG_XFS_WARN 2013-05-07 18:45:36 -05:00
uuid.c
…
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 block: remove bio_get_nr_vecs() 2015-08-13 12:32:04 -06:00
xfs_aops.h xfs: add DAX file operations support 2015-06-04 09:18:53 +10:00
xfs_attr.h xfs: kill xfs_vnodeops.[ch] 2013-08-12 16:53:39 -05:00
xfs_attr_inactive.c Merge branch 'xfs-misc-fixes-for-4.2-3' into for-next 2015-06-23 08:49:01 +10:00
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-commit-cleanup' into for-next 2015-06-04 13:55:48 +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 block: add a bi_error field to struct bio 2015-07-29 08:55:15 -06:00
xfs_buf.h xfs: return a void pointer from xfs_buf_offset 2015-06-22 09:44:29 +10:00
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_dquot.c xfs: saner xfs_trans_commit interface 2015-06-04 13:48:08 +10:00
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: remove inst_t 2015-06-22 09:44:02 +10:00
xfs_error.h xfs: remove inst_t 2015-06-22 09:44:02 +10:00
xfs_export.c VFS: normal filesystems (and lustre): d_inode() annotations 2015-04-15 15:06:57 -04:00
xfs_export.h
…
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: remove __psint_t and __psunsigned_t 2015-06-22 09:43:32 +10:00
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: call dax_fault on read page faults for DAX 2015-07-29 11:48:00 +10:00
xfs_filestream.c xfs: clean up XFS_MIN_FREELIST macros 2015-06-22 10:13:30 +10:00
xfs_filestream.h xfs: add filestream allocator tracepoints 2014-04-23 07:11:52 +10:00
xfs_fsops.c Merge branch 'xfs-commit-cleanup' into for-next 2015-06-04 13:55:48 +10:00
xfs_fsops.h
…
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 Merge branch 'xfs-misc-fixes-for-4.2-3' into for-next 2015-06-23 08:49:01 +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 xfs: saner xfs_trans_commit interface 2015-06-04 13:48:08 +10:00
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: saner xfs_trans_commit interface 2015-06-04 13:48:08 +10:00
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 xfs: update for 4.2-rc1 2015-06-30 20:16:08 -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: use actual inode count for sparse records in bulkstat/inumbers 2015-05-29 09:04:19 +10:00
xfs_itable.h xfs: bulkstat chunk formatting cursor is broken 2014-11-07 08:30:30 +11:00
xfs_linux.h xfs: remove xfs_caddr_t 2015-06-22 09:45:10 +10:00
xfs_log.c Merge branch 'xfs-misc-fixes-for-4.2-3' into for-next 2015-06-23 08:49:01 +10:00
xfs_log.h xfs: fix xfs_log_done interface 2015-06-04 13:48:20 +10:00
xfs_log_cil.c xfs: fix xfs_log_done interface 2015-06-04 13:48:20 +10:00
xfs_log_priv.h xfs: use void pointers in log validation helpers 2015-06-22 09:44:47 +10:00
xfs_log_recover.c xfs: remote attribute headers contain an invalid LSN 2015-07-29 11:48:01 +10:00
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 Merge branch 'xfs-sparse-inode' into for-next 2015-06-01 10:51:38 +10:00
xfs_mount.h Merge branch 'xfs-dax-support' into for-next 2015-06-04 13:01:49 +10:00
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 xfs: saner xfs_trans_commit interface 2015-06-04 13:48:08 +10:00
xfs_pnfs.h xfs: unlock i_mutex in xfs_break_layouts 2015-04-13 11:38:29 +10:00
xfs_qm.c xfs: saner xfs_trans_commit interface 2015-06-04 13:48:08 +10:00
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: saner xfs_trans_commit interface 2015-06-04 13:48:08 +10:00
xfs_quota.h xfs: fix quota block reservation leak when tp allocates and frees blocks 2015-06-01 07:15:37 +10:00
xfs_quotaops.c xfs: Add support for Q_SETINFO 2015-03-04 16:06:38 +01:00
xfs_rtalloc.c xfs: saner xfs_trans_commit interface 2015-06-04 13:48:08 +10:00
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 2015-09-04 16:54:41 -07:00
xfs_super.h xfs: Remove icsb infrastructure 2015-02-23 21:22:31 +11:00
xfs_symlink.c Merge branch 'xfs-misc-fixes-for-4.2-3' into for-next 2015-06-23 08:49:01 +10:00
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 xfs: allocate sparse inode chunks on full chunk allocation failure 2015-05-29 09:18:32 +10:00
xfs_trans.c xfs: fix xfs_log_done interface 2015-06-04 13:48:20 +10:00
xfs_trans.h xfs: saner xfs_trans_commit interface 2015-06-04 13:48:08 +10:00
xfs_trans_ail.c xfs: remove __psint_t and __psunsigned_t 2015-06-22 09:43:32 +10:00
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: Clean up xfs_trans_dup_dqinfo 2015-06-01 10:50:00 +10:00
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: pass a boolean flag to xfs_trans_free_items 2015-06-04 13:47:43 +10:00
xfs_xattr.c VFS: normal filesystems (and lustre): d_inode() annotations 2015-04-15 15:06:57 -04:00