| From e9c243a5a6de0be8e584c604d353412584b592f8 Mon Sep 17 00:00:00 2001 |
| From: Thomas Gleixner <tglx@linutronix.de> |
| Date: Tue, 3 Jun 2014 12:27:06 +0000 |
| Subject: futex-prevent-requeue-pi-on-same-futex.patch futex: Forbid uaddr == uaddr2 in futex_requeue(..., requeue_pi=1) |
| |
| From: Thomas Gleixner <tglx@linutronix.de> |
| |
| commit e9c243a5a6de0be8e584c604d353412584b592f8 upstream. |
| |
| 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 6f7b0a2a5c0f ("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> |
| 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> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| kernel/futex.c | 25 +++++++++++++++++++++++++ |
| 1 file changed, 25 insertions(+) |
| |
| --- a/kernel/futex.c |
| +++ b/kernel/futex.c |
| @@ -1293,6 +1293,13 @@ static int futex_requeue(u32 __user *uad |
| |
| 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. |
| */ |
| @@ -1330,6 +1337,15 @@ 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); |
| |
| @@ -2360,6 +2376,15 @@ static int futex_wait_requeue_pi(u32 __u |
| 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); |
| |