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 tiwai@suse.de 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 syzkaller@googlegroups.com Cc: stable@vger.kernel.org Signed-off-by: Takashi Iwai tiwai@suse.de --- 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;