kernel-ark/net/ceph
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
..
crush crush: sync up with userspace 2015-06-25 11:49:31 +03:00
armor.c
auth_none.c
auth_none.h
auth_x_protocol.h
auth_x.c libceph: fix sparse endianness warnings 2015-01-08 20:36:57 +03:00
auth_x.h libceph: store session key in cephx authorizer 2014-12-17 20:09:50 +03:00
auth.c
buffer.c libceph: nuke ceph_kvfree() 2014-12-17 20:09:50 +03:00
ceph_common.c fs: create and use seq_show_option for escaping 2015-09-04 16:54:41 -07:00
ceph_fs.c
ceph_hash.c
ceph_strings.c libceph: nuke pool op infrastructure 2015-02-19 13:31:37 +03:00
crypto.c libceph: do not crash on large auth tickets 2014-11-13 22:21:12 +03:00
crypto.h
debugfs.c libceph: expose client options through debugfs 2015-04-20 18:55:39 +03:00
Kconfig
Makefile
messenger.c libceph: treat sockaddr_storage with uninitialized family as blank 2015-07-09 20:30:34 +03:00
mon_client.c libceph: a couple tweaks for wait loops 2015-06-25 11:49:29 +03:00
msgpool.c
osd_client.c libceph: store timeouts in jiffies, verify user input 2015-06-25 11:49:29 +03:00
osdmap.c crush: fix a bug in tree bucket decode 2015-07-01 00:46:35 +03:00
pagelist.c
pagevec.c libceph: use kvfree() instead of open-coding it 2015-06-25 11:49:28 +03:00
snapshot.c