[PATCH v3 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, so address this by adding the governor cleanup to
the rollback path.

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, so address it by placing the cleanup thermal_set_governor()
call after the wait_for_completion() one, which reflects the
registration error path ordering.

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>
---

v2 -> v3: New patch

---
 drivers/thermal/thermal_core.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -1618,7 +1618,7 @@ thermal_zone_device_register_with_trips(
 	/* Add nodes that are always present via .groups */
 	result = thermal_zone_create_device_groups(tz);
 	if (result)
-		goto remove_id;
+		goto remove_governor;
 
 	result = device_register(&tz->device);
 	if (result)
@@ -1649,6 +1649,8 @@ unregister:
 release_device:
 	put_device(&tz->device);
 	wait_for_completion(&tz->removal);
+remove_governor:
+	thermal_set_governor(tz, NULL);
 remove_id:
 	ida_free(&thermal_tz_ida, id);
 free_tzp:
@@ -1731,8 +1733,6 @@ 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);
@@ -1744,6 +1744,9 @@ void thermal_zone_device_unregister(stru
 	thermal_notify_tz_delete(tz);
 
 	wait_for_completion(&tz->removal);
+
+	thermal_set_governor(tz, NULL);
+
 	kfree(tz->tzp);
 	kfree(tz);
 }