exec: pin stack limit during exec
authorKees Cook <keescook@chromium.org>
Tue, 10 Apr 2018 23:35:01 +0000 (16:35 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Wed, 11 Apr 2018 17:28:37 +0000 (10:28 -0700)
commitc31dbb146dd44af44bc60780ce8fa7a9f5f746df
treeac3f22913cec3082511ab9143d153ad30975a884
parentb83838313386f617d6bd8201be7f5b532059bba1
exec: pin stack limit during exec

Since the stack rlimit is used in multiple places during exec and it can
be changed via other threads (via setrlimit()) or processes (via
prlimit()), the assumption that the value doesn't change cannot be made.
This leads to races with mm layout selection and argument size
calculations.  This changes the exec path to use the rlimit stored in
bprm instead of in current.  Before starting the thread, the bprm stack
rlimit is stored back to current.

Link: http://lkml.kernel.org/r/1518638796-20819-4-git-send-email-keescook@chromium.org
Fixes: 64701dee4178e ("exec: Use sane stack rlimit under secureexec")
Signed-off-by: Kees Cook <keescook@chromium.org>
Reported-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Reported-by: Andy Lutomirski <luto@kernel.org>
Reported-by: Brad Spengler <spender@grsecurity.net>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: Greg KH <greg@kroah.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fs/exec.c
include/linux/binfmts.h