[37/90] ALSA: timer - Fix Oops at closing slave timer

[Greg KH]

3.0-stable review patch.  If anyone has any objections, please let us know.

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

From: Takashi Iwai <tiwai@xxxxxxx>

commit 0584ffa548b6e59aceb027112f23a55f0133400e upstream.

A slave-timer instance has no timer reference, and this results in
NULL-dereference at stopping the timer, typically called at closing
the device.

Reference: https://bugzilla.kernel.org/show_bug.cgi?id=40682

Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 sound/core/timer.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/sound/core/timer.c
+++ b/sound/core/timer.c
@@ -531,6 +531,8 @@ int snd_timer_stop(struct snd_timer_inst
 	if (err < 0)
 		return err;
 	timer = timeri->timer;
+	if (!timer)
+		return -EINVAL;
 	spin_lock_irqsave(&timer->lock, flags);
 	timeri->cticks = timeri->ticks;
 	timeri->pticks = 0;


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