From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756326AbbCLTi3 (ORCPT ); Thu, 12 Mar 2015 15:38:29 -0400 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.229]:31573 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754154AbbCLTON (ORCPT ); Thu, 12 Mar 2015 15:14:13 -0400 Message-Id: <20150312191409.707856750@goodmis.org> User-Agent: quilt/0.61-1 Date: Thu, 12 Mar 2015 15:13:23 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org, linux-rt-users Cc: Thomas Gleixner , Carsten Emde , Sebastian Andrzej Siewior , John Kacur , Paul Gortmaker , Subject: [PATCH RT 16/39] locking/rt-mutex: avoid a NULL pointer dereference on deadlock References: <20150312191307.081068717@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Disposition: inline; filename=0016-locking-rt-mutex-avoid-a-NULL-pointer-dereference-on.patch X-RR-Connecting-IP: 107.14.168.142:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.14.34-rt32-rc1 stable review patch. If anyone has any objections, please let me know. ------------------ From: Sebastian Andrzej Siewior With task_blocks_on_rt_mutex() returning early -EDEADLK we never add the waiter to the waitqueue. Later, we try to remove it via remove_waiter() and go boom in rt_mutex_top_waiter() because rb_entry() gives a NULL pointer. Tested on v3.18-RT where rtmutex is used for regular mutex and I tried to get one twice in a row. Not sure when this started but I guess 397335f00 ("rtmutex: Fix deadlock detector for real") or commit 3d5c9340 ("rtmutex: Handle deadlock detection smarter"). Cc: stable-rt@vger.kernel.org Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Steven Rostedt --- kernel/locking/rtmutex.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index a0d9eadcfe02..ec72272ab73a 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -1697,7 +1697,8 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state, set_current_state(TASK_RUNNING); if (unlikely(ret)) { - remove_waiter(lock, &waiter); + if (rt_mutex_has_waiters(lock)) + remove_waiter(lock, &waiter); rt_mutex_handle_deadlock(ret, chwalk, &waiter); } else if (ww_ctx) { ww_mutex_account_lock(lock, ww_ctx); -- 2.1.4