From: Thomas Gleixner <tglx@linutronix.de>
Date: Thu, 11 Sep 2014 21:44:35 +0000 (+0200)
Subject: futex: Unlock hb->lock in futex_wait_requeue_pi() error path
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=0652fc95fb0fa0f35cd4abad26f5eabc0ecf64a3;p=karo-tx-linux.git

futex: Unlock hb->lock in futex_wait_requeue_pi() error path

commit 13c42c2f43b19aab3195f2d357db00d1e885eaa8 upstream.

futex_wait_requeue_pi() calls futex_wait_setup(). If
futex_wait_setup() succeeds it returns with hb->lock held and
preemption disabled. Now the sanity check after this does:

        if (match_futex(&q.key, &key2)) {
	   	ret = -EINVAL;
		goto out_put_keys;
	}

which releases the keys but does not release hb->lock.

So we happily return to user space with hb->lock held and therefor
preemption disabled.

Unlock hb->lock before taking the exit route.

Reported-by: Dave "Trinity" Jones <davej@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Darren Hart <dvhart@linux.intel.com>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1409112318500.4178@nanos
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/kernel/futex.c b/kernel/futex.c
index e3087afb7429..0b0dc02aabce 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2614,6 +2614,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
 	 * shared futexes. We need to compare the keys:
 	 */
 	if (match_futex(&q.key, &key2)) {
+		queue_unlock(hb);
 		ret = -EINVAL;
 		goto out_put_keys;
 	}