ASoC: SOF: Protect swidget->use_count with mutex for kcontrol access race

The use_count of the swidget is protect by ALSA core PCM locking with the
exception when an associated kcontrol is changed.

It has been observed that a rightly timed kcontrol access during stream
stop can result of an attempt to send a control update to a widget which
has been freed up between the check of the use_count and the message
sending.

We need to protect the entire sof_widget_setup() and sof_widget_free()
execution to make it safe to rely on the use_count.
Move the code under an _unlocked() function and use a mutex to protect
the execution of the functions for concurrency.
On the control path we need to use the lock only for the kcontrol access,
the widget_kcontrol_setup() op is called with the lock already held.

Reported-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Link: https://lore.kernel.org/r/20230127120031.10709-18-peter.ujfalusi@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/sound/soc/sof/ipc3-topology.c b/sound/soc/sof/ipc3-topology.c
index 88b9b9507231..dceb78bfe17c 100644
--- a/sound/soc/sof/ipc3-topology.c
+++ b/sound/soc/sof/ipc3-topology.c
@@ -2316,7 +2316,9 @@ static int sof_ipc3_tear_down_all_pipelines(struct snd_sof_dev *sdev, bool verif
 		/* Do not free widgets for static pipelines with FW older than SOF2.2 */
 		if (!verify && !swidget->dynamic_pipeline_widget &&
 		    SOF_FW_VER(v->major, v->minor, v->micro) < SOF_FW_VER(2, 2, 0)) {
+			mutex_lock(&swidget->setup_mutex);
 			swidget->use_count = 0;
+			mutex_unlock(&swidget->setup_mutex);
 			if (swidget->spipe)
 				swidget->spipe->complete = 0;
 			continue;