linux_dsm_epyc7002/security/selinux
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
..
include Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2015-06-27 13:26:03 -07:00
ss selinux: don't waste ebitmap space when importing NetLabel categories 2015-07-09 14:20:36 -04:00
.gitignore SELinux: add .gitignore files for dynamic classes 2009-10-24 09:42:27 +08:00
avc.c security/selinux: pass 'flags' arg to avc_audit() and avc_has_perm_flags() 2015-05-11 08:13:11 -04:00
exports.c selinux: sparse fix: include selinux.h in exports.c 2011-09-09 16:56:32 -07:00
hooks.c fs: create and use seq_show_option for escaping 2015-09-04 16:54:41 -07:00
Kconfig selinux: Deprecate and schedule the removal of the the compat_net functionality 2008-12-31 12:54:11 -05:00
Makefile selinux: change to new flag variable 2010-10-21 10:12:40 +11:00
netif.c Merge commit 'v3.17' into next 2014-11-19 21:32:12 +11:00
netlabel.c selinux: ensure that the cached NetLabel secattr matches the desired SID 2013-12-04 16:08:17 -05:00
netlink.c selinux: replace obsolete NLMSG_* with type safe nlmsg_* 2013-03-28 14:25:49 -04:00
netnode.c selinux: remove unused variabled in the netport, netnode, and netif caches 2014-08-07 20:55:30 -04:00
netport.c selinux: remove unused variabled in the netport, netnode, and netif caches 2014-08-07 20:55:30 -04:00
nlmsgtab.c selinux/nlmsg: add a build time check for rtnl/xfrm cmds 2015-04-13 13:09:44 -04:00
selinuxfs.c sysfs: Create mountpoints with sysfs_create_mount_point 2015-07-01 10:36:47 -05:00
xfrm.c netfilter: Remove spurios included of netfilter.h 2015-06-18 21:14:32 +02:00