From: Takashi Iwai <tiwai@suse.de>
Date: Thu, 30 Nov 2017 09:08:28 +0000 (+0100)
Subject: ALSA: seq: Remove spurious WARN_ON() at timer check
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=8a4b29a72a7cac97a44dec1b74ec804e0176cca8;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git

ALSA: seq: Remove spurious WARN_ON() at timer check

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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

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;