git.ipfire.org Git - thirdparty/kernel/stable-queue.git/blob

   1 From e9c243a5a6de0be8e584c604d353412584b592f8 Mon Sep 17 00:00:00 2001
   2 From: Thomas Gleixner <tglx@linutronix.de>
   3 Date: Tue, 3 Jun 2014 12:27:06 +0000
   4 Subject: futex-prevent-requeue-pi-on-same-futex.patch futex: Forbid uaddr == uaddr2 in futex_requeue(..., requeue_pi=1)
   5
   6 From: Thomas Gleixner <tglx@linutronix.de>
   7
   8 commit e9c243a5a6de0be8e584c604d353412584b592f8 upstream.
   9
  10 If uaddr == uaddr2, then we have broken the rule of only requeueing from
  11 a non-pi futex to a pi futex with this call.  If we attempt this, then
  12 dangling pointers may be left for rt_waiter resulting in an exploitable
  13 condition.
  14
  15 This change brings futex_requeue() in line with futex_wait_requeue_pi()
  16 which performs the same check as per commit 6f7b0a2a5c0f ("futex: Forbid
  17 uaddr == uaddr2 in futex_wait_requeue_pi()")
  18
  19 [ tglx: Compare the resulting keys as well, as uaddrs might be
  20         different depending on the mapping ]
  21
  22 Fixes CVE-2014-3153.
  23
  24 Reported-by: Pinkie Pie
  25 Signed-off-by: Will Drewry <wad@chromium.org>
  26 Signed-off-by: Kees Cook <keescook@chromium.org>
  27 Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
  28 Reviewed-by: Darren Hart <dvhart@linux.intel.com>
  29 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  30 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  31
  32 ---
  33  kernel/futex.c |   25 +++++++++++++++++++++++++
  34  1 file changed, 25 insertions(+)
  35
  36 --- a/kernel/futex.c
  37 +++ b/kernel/futex.c
  38 @@ -1428,6 +1428,13 @@ static int futex_requeue(u32 __user *uad
  39
  40         if (requeue_pi) {
  41                 /*
  42 +                * Requeue PI only works on two distinct uaddrs. This
  43 +                * check is only valid for private futexes. See below.
  44 +                */
  45 +               if (uaddr1 == uaddr2)
  46 +                       return -EINVAL;
  47 +
  48 +               /*
  49                  * requeue_pi requires a pi_state, try to allocate it now
  50                  * without any locks in case it fails.
  51                  */
  52 @@ -1465,6 +1472,15 @@ retry:
  53         if (unlikely(ret != 0))
  54                 goto out_put_key1;
  55
  56 +       /*
  57 +        * The check above which compares uaddrs is not sufficient for
  58 +        * shared futexes. We need to compare the keys:
  59 +        */
  60 +       if (requeue_pi && match_futex(&key1, &key2)) {
  61 +               ret = -EINVAL;
  62 +               goto out_put_keys;
  63 +       }
  64 +
  65         hb1 = hash_futex(&key1);
  66         hb2 = hash_futex(&key2);
  67
  68 @@ -2511,6 +2527,15 @@ static int futex_wait_requeue_pi(u32 __u
  69         if (ret)
  70                 goto out_key2;
  71
  72 +       /*
  73 +        * The check above which compares uaddrs is not sufficient for
  74 +        * shared futexes. We need to compare the keys:
  75 +        */
  76 +       if (match_futex(&q.key, &key2)) {
  77 +               ret = -EINVAL;
  78 +               goto out_put_keys;
  79 +       }
  80 +
  81         /* Queue the futex_q, drop the hb lock, wait for wakeup. */
  82         futex_wait_queue_me(hb, &q, to);
  83