From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752013AbdK3JPG (ORCPT ); Thu, 30 Nov 2017 04:15:06 -0500 Received: from mx2.suse.de ([195.135.220.15]:45281 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750849AbdK3JPE (ORCPT ); Thu, 30 Nov 2017 04:15:04 -0500 Date: Thu, 30 Nov 2017 10:15:02 +0100 Message-ID: From: Takashi Iwai To: syzbot Cc: , , , Subject: Re: WARNING in initialize_timer In-Reply-To: <001a1148cc3adcd1e9055f2cf29a@google.com> References: <001a1148cc3adcd1e9055f2cf29a@google.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/25.3 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 30 Nov 2017 06:59:01 +0100, syzbot wrote: > > Hello, > > syzkaller hit the following crash on > 43570f0383d6d5879ae585e6c3cf027ba321546f > git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master > compiler: gcc (GCC) 7.1.1 20170620 > .config is attached > Raw console output is attached. > > Unfortunately, I don't have any reproducer for this bug yet. > > > binder: 4519:4521 ioctl 40046205 2 returned -22 > binder: 4519:4521 ioctl c0106403 20008ff0 returned -22 > WARNING: CPU: 0 PID: 4528 at sound/core/seq/seq_timer.c:358 > initialize_timer+0x22d/0x290 sound/core/seq/seq_timer.c:358 This must be a spurious WARN_ON() when a slave timer is used while the master is freed. I'm going to queue the patch below. #syz fix: ALSA: seq: Remove spurious WARN_ON() at timer check thanks, Takashi -- 8< -- From: Takashi Iwai Subject: [PATCH] ALSA: seq: Remove spurious WARN_ON() at timer check The use of snd_BUG_ON() in ALSA sequencer timer may lead to a spurious WARN_ON() when a slave timer is deployed as its backend and a corresponding master timer stops meanwhile. The symptom was triggered by syzkaller spontaneously. Since the NULL timer is valid there, rip off snd_BUG_ON(). Reported-by: syzbot Cc: Signed-off-by: Takashi Iwai --- sound/core/seq/seq_timer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/sound/core/seq/seq_timer.c b/sound/core/seq/seq_timer.c index 37d9cfbc29f9..b80985fbc334 100644 --- a/sound/core/seq/seq_timer.c +++ b/sound/core/seq/seq_timer.c @@ -355,7 +355,7 @@ static int initialize_timer(struct snd_seq_timer *tmr) unsigned long freq; t = tmr->timeri->timer; - if (snd_BUG_ON(!t)) + if (!t) return -EINVAL; freq = tmr->preferred_resolution; -- 2.15.0