ALSA: timer: Fix master timer notification

stable inclusion
from stable-5.10.43
commit 029c06103e0ad669e6bec74f26b006198041326d
bugzilla: 109284
CVE: NA

--------------------------------

commit 9c1fe96b upstream.

snd_timer_notify1() calls the notification to each slave for a master
event, but it passes a wrong event number.  It should be +10 offset,
corresponding to SNDRV_TIMER_EVENT_MXXX, but it's incorrectly with
+100 offset.  Casually this was spotted by UBSAN check via syzkaller.

Reported-by: syzbot+d102fa5b35335a7e544e@syzkaller.appspotmail.com
Reviewed-by: NJaroslav Kysela <perex@perex.cz>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/000000000000e5560e05c3bd1d63@google.com
Link: https://lore.kernel.org/r/20210602113823.23777-1-tiwai@suse.deSigned-off-by: NTakashi Iwai <tiwai@suse.de>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

sound/core/timer.c

@@ -520,9 +520,10 @@ static void snd_timer_notify1(struct snd_timer_instance *ti, int event)
 		return;
 	if (timer->hw.flags & SNDRV_TIMER_HW_SLAVE)
 		return;
+	event += 10; /* convert to SNDRV_TIMER_EVENT_MXXX */
 	list_for_each_entry(ts, &ti->slave_active_head, active_list)
 		if (ts->ccallback)
-			ts->ccallback(ts, event + 100, &tstamp, resolution);
+			ts->ccallback(ts, event, &tstamp, resolution);
 }
 
 /* start/continue a master timer */