[PATCH v4 1/6] thermal: core: Fix thermal zone governor cleanup issues

[Rafael J. Wysocki]

From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

If thermal_zone_device_register_with_trips() fails after adding
a thermal governor to the thermal zone being registered, the
governor is not removed from it as appropriate which may lead to
a memory leak.

In turn, thermal_zone_device_unregister() calls thermal_set_governor()
without acquiring the thermal zone lock beforehand which may race with
a governor update via sysfs and may lead to a use-after-free in that
case.

Address these issues by adding two thermal_set_governor() calls, one to
thermal_release() to remove the governor from the given thermal zone,
and one to the thermal zone registration error path to cover failures
preceding the thermal zone device registration.

Fixes: e33df1d2f3a0 ("thermal: let governors have private data for each thermal zone")
Cc: All applicable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
---

v3 -> v4:
   * Call thermal_set_governor() from thermal_release() to avoid use-after-free
     of the device name (Sashiko)
   * Call thermal_set_governor() in thermal zone device registration rollback
     path if it fails before device registration

v2 -> v3: New patch

---
 drivers/thermal/thermal_core.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -971,6 +971,7 @@ static void thermal_release(struct devic
 		     sizeof("thermal_zone") - 1)) {
 		tz = to_thermal_zone(dev);
 		thermal_zone_destroy_device_groups(tz);
+		thermal_set_governor(tz, NULL);
 		mutex_destroy(&tz->lock);
 		complete(&tz->removal);
 	} else if (!strncmp(dev_name(dev), "cooling_device",
@@ -1617,8 +1618,10 @@ thermal_zone_device_register_with_trips(
 	/* sys I/F */
 	/* Add nodes that are always present via .groups */
 	result = thermal_zone_create_device_groups(tz);
-	if (result)
+	if (result) {
+		thermal_set_governor(tz, NULL);
 		goto remove_id;
+	}
 
 	result = device_register(&tz->device);
 	if (result)
@@ -1731,8 +1734,6 @@ void thermal_zone_device_unregister(stru
 
 	cancel_delayed_work_sync(&tz->poll_queue);
 
-	thermal_set_governor(tz, NULL);
-
 	thermal_thresholds_exit(tz);
 	thermal_remove_hwmon_sysfs(tz);
 	ida_free(&thermal_tz_ida, tz->id);