ALSA: pcmtest: stop timer before buffer is released

Stop timer in the 'trigger' and 'sync_stop' callbacks since we want
the timer to be stopped before the DMA buffer is released. Otherwise,
it could trigger a kernel panic in some circumstances, for instance
when the DMA buffer is already released but the timer callback is
still running.

Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com>
Link: https://lore.kernel.org/r/20231206223211.12761-1-ivan.orlov0322@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>

Author: ivanorlov2206

sound/drivers/pcmtest.c

@@ -397,7 +397,6 @@ static int snd_pcmtst_pcm_close(struct snd_pcm_substream *substream)
 	struct pcmtst_buf_iter *v_iter = substream->runtime->private_data;
 
 	timer_shutdown_sync(&v_iter->timer_instance);
-	v_iter->substream = NULL;
 	playback_capture_test = !v_iter->is_buf_corrupted;
 	kfree(v_iter);
 	return 0;
@@ -435,6 +434,7 @@ static int snd_pcmtst_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
 	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
 		// We can't call timer_shutdown_sync here, as it is forbidden to sleep here
 		v_iter->suspend = true;
+		timer_delete(&v_iter->timer_instance);
 		break;
 	}
 
@@ -512,12 +512,22 @@ static int snd_pcmtst_ioctl(struct snd_pcm_substream *substream, unsigned int cm
 	return snd_pcm_lib_ioctl(substream, cmd, arg);
 }
 
+static int snd_pcmtst_sync_stop(struct snd_pcm_substream *substream)
+{
+	struct pcmtst_buf_iter *v_iter = substream->runtime->private_data;
+
+	timer_delete_sync(&v_iter->timer_instance);
+
+	return 0;
+}
+
 static const struct snd_pcm_ops snd_pcmtst_playback_ops = {
 	.open =		snd_pcmtst_pcm_open,
 	.close =	snd_pcmtst_pcm_close,
 	.trigger =	snd_pcmtst_pcm_trigger,
 	.hw_params =	snd_pcmtst_pcm_hw_params,
 	.ioctl =	snd_pcmtst_ioctl,
+	.sync_stop =	snd_pcmtst_sync_stop,
 	.hw_free =	snd_pcmtst_pcm_hw_free,
 	.prepare =	snd_pcmtst_pcm_prepare,
 	.pointer =	snd_pcmtst_pcm_pointer,
@@ -530,6 +540,7 @@ static const struct snd_pcm_ops snd_pcmtst_capture_ops = {
 	.hw_params =	snd_pcmtst_pcm_hw_params,
 	.hw_free =	snd_pcmtst_pcm_hw_free,
 	.ioctl =	snd_pcmtst_ioctl,
+	.sync_stop =	snd_pcmtst_sync_stop,
 	.prepare =	snd_pcmtst_pcm_prepare,
 	.pointer =	snd_pcmtst_pcm_pointer,
 };