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-Tag: v3.2.64~61
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2e10b8a67f891a1d9b86ca72321259a7f63d3b42;p=thirdparty%2Fkernel%2Fstable.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>
[bwh: Backported to 3.2: queue_unlock() takes two parameters]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

diff --git a/kernel/futex.c b/kernel/futex.c
index 1bb37d0f3d7a9..f31f190ef4c46 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2460,6 +2460,7 @@ 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(&q, hb);
 		ret = -EINVAL;
 		goto out_put_keys;
 	}