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authorThomas Gleixner <tglx@linutronix.de>2014-06-03 12:27:06 (GMT)
committerPaul Kocialkowski <contact@paulk.fr>2014-07-17 14:46:53 (GMT)
commit4c52bc8a2ff3c0373d371995eaef34df98e1fa4c (patch)
tree57628814511eec6890bc5fe3820b42f745bd1f44
parent792bf04d04ba529e6aa1267eeae5361e02980f28 (diff)
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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 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 ] Change-Id: Ibe6195215657c86bf2e39305656fdacf7230389d 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>
-rw-r--r--kernel/futex.c25
1 files changed, 25 insertions, 0 deletions
diff --git a/kernel/futex.c b/kernel/futex.c
index 61e554e..ec372fd 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1271,6 +1271,13 @@ 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.
*/
@@ -1308,6 +1315,15 @@ 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);
@@ -2330,6 +2346,15 @@ 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);