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futex-prevent-requeue-pi-on-same-futex.patch futex: Forbid uaddr == uaddr2 in futex_requeue(..., requeue_pi=1) 

If uaddr == uaddr2, then we have broken the rule of only requeueing from
a non-pi futex to a pi futex with this call.  If we attempt this, then
dangling pointers may be left for rt_waiter resulting in an exploitable
condition.

This change brings futex_requeue() in line with futex_wait_requeue_pi()
which performs the same check as per commit 6f7b0a2a5c ("futex: Forbid
uaddr == uaddr2 in futex_wait_requeue_pi()")

[ tglx: Compare the resulting keys as well, as uaddrs might be
  	different depending on the mapping ]

Fixes CVE-2014-3153.

Reported-by: Pinkie Pie
Signed-off-by: Will Drewry <wad@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Darren Hart <dvhart@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Thomas Gleixner 2014-06-03 12:27:06 +00:00 committed by Linus Torvalds
parent fad01e866a
commit e9c243a5a6
1 changed files with 25 additions and 0 deletions
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25
kernel/futex.c
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@ -1441,6 +1441,13 @@ static int futex_requeue(u32 __user *uaddr1, unsigned int flags,
struct futex_q *this, *next;
if (requeue_pi) {
/*
* Requeue PI only works on two distinct uaddrs. This
* check is only valid for private futexes. See below.
*/
if (uaddr1 == uaddr2)
return -EINVAL;
/*
* requeue_pi requires a pi_state, try to allocate it now
* without any locks in case it fails.
@ -1479,6 +1486,15 @@ retry:
if (unlikely(ret != 0))
goto out_put_key1;
/*
* The check above which compares uaddrs is not sufficient for
* shared futexes. We need to compare the keys:
*/
if (requeue_pi && match_futex(&key1, &key2)) {
ret = -EINVAL;
goto out_put_keys;
}
hb1 = hash_futex(&key1);
hb2 = hash_futex(&key2);
@ -2525,6 +2541,15 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
if (ret)
goto out_key2;
/*
* The check above which compares uaddrs is not sufficient for
* shared futexes. We need to compare the keys:
*/
if (match_futex(&q.key, &key2)) {
ret = -EINVAL;
goto out_put_keys;
}
/* Queue the futex_q, drop the hb lock, wait for wakeup. */
futex_wait_queue_me(hb, &q, to);