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/topology.c b/sound/soc/sof/topology.c
index 33ca3067262b..e2f8cd9e278e 100644
--- a/sound/soc/sof/topology.c
+++ b/sound/soc/sof/topology.c
@@ -1405,6 +1405,8 @@ static int sof_widget_ready(struct snd_soc_component *scomp, int index,
 	swidget->id = w->id;
 	swidget->pipeline_id = index;
 	swidget->private = NULL;
+	mutex_init(&swidget->setup_mutex);
+
 	ida_init(&swidget->src_queue_ida);
 	ida_init(&swidget->sink_queue_ida);