linux-kernel - [ 47/48] futex: Unlock hb->lock in futex_wait_requeue

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20141116215330.610444402@1wt.eu>
Date:	Sun, 16 Nov 2014 22:54:15 +0100
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Willy Tarreau <w@....eu>
Subject: [ 47/48] futex: Unlock hb->lock in futex_wait_requeue_pi()

2.6.32-longterm review patch.  If anyone has any objections, please let me know.

------------------
 error path

From: Thomas Gleixner <tglx@...utronix.de>

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@...hat.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Darren Hart <dvhart@...ux.intel.com>
Reviewed-by: Davidlohr Bueso <dave@...olabs.net>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: stable@...r.kernel.org
Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1409112318500.4178@nanos
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
(cherry picked from commit 13c42c2f43b19aab3195f2d357db00d1e885eaa8)
[wt: 2.6.32 needs &q as first argument of queue_unlock()]
Signed-off-by: Willy Tarreau <w@....eu>
---
 kernel/futex.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/futex.c b/kernel/futex.c
index 55dd3d2..1e092d3 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2414,6 +2414,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, int fshared,
 	 * shared futexes. We need to compare the keys:
 	 */
 	if (match_futex(&q.key, &key2)) {
+		queue_unlock(&q, hb);
 		ret = -EINVAL;
 		goto out_put_keys;
 	}
-- 
1.7.12.2.21.g234cd45.dirty



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/