[PATCH 3.2 021/140] ALSA: seq: Remove spurious WARN_ON() at timer check

Ben Hutchings
2018-02-28T16:26:17Z

From: Takashi Iwai <tiwai@suse.de>

commit 43a3542870328601be02fcc9d27b09db467336ef upstream.

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>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
sound/core/seq/seq_timer.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/sound/core/seq/seq_timer.c
+++ b/sound/core/seq/seq_timer.c
@@ -357,7 +357,7 @@ static int initialize_timer(struct snd_s
unsigned long freq;

t = tmr->timeri->timer;
- if (snd_BUG_ON(!t))
+ if (!t)
return -EINVAL;

freq = tmr->preferred_resolution;