source: trunk/server/common/patches/cve-2014-3153-1.patch @ 2581

From b58623fb64ff0454ec20bce7a02275a20c23086d Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 3 Jun 2014 12:27:06 +0000
Subject: [PATCH 1/4] futex-prevent-requeue-pi-on-same-futex.patch futex:
 Forbid uaddr == uaddr2 in futex_requeue(...,
 requeue_pi=1)

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(+)

diff --git a/kernel/futex.c b/kernel/futex.c
index 58743c0..93e522f 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1293,6 +1293,13 @@ static int futex_requeue(u32 __user *uaddr1, unsigned int flags,
 
        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 __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);
 
-- 
1.7.10.4