thermal/core/fair share: Lock the thermal zone while looping over instances

commit fef05776 upstream.

The tz->lock must be hold during the looping over the instances in that
thermal zone. This lock was missing in the governor code since the
beginning, so it's hard to point into a particular commit.

CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20210422153624.6074-2-lukasz.luba@arm.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/thermal/gov_fair_share.c

@@ -82,6 +82,8 @@ static int fair_share_throttle(struct thermal_zone_device *tz, int trip)
 	int total_instance = 0;
 	int cur_trip_level = get_trip_level(tz);
 
+	mutex_lock(&tz->lock);
+
 	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
 		if (instance->trip != trip)
 			continue;
@@ -110,6 +112,8 @@ static int fair_share_throttle(struct thermal_zone_device *tz, int trip)
 		mutex_unlock(&instance->cdev->lock);
 		thermal_cdev_update(cdev);
 	}
+
+	mutex_unlock(&tz->lock);
 	return 0;
 }