[PATCH v1] thermal: core: Fix use-after-free in thermal_zone_device_unregister()

[Dmitry Osipenko]

The user-after-free bug in thermal_zone_device_unregister() is reported by
KASAN. It happens because struct thermal_zone_device is released during of
device_unregister() invocation, and hence the "tz" variable shouldn't be
touched by thermal_notify_tz_delete(tz->id).

Fixes: 55cdf0a283b8 ("thermal: core: Add notifications call in the framework")
Signed-off-by: Dmitry Osipenko <dig...@gmail.com>
---
 drivers/thermal/thermal_core.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index 72bf159bcecc..56c355f684df 100644
--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -1516,7 +1516,7 @@ EXPORT_SYMBOL_GPL(thermal_zone_device_register);
  */
 void thermal_zone_device_unregister(struct thermal_zone_device *tz)
 {
-       int i;
+       int i, tz_id;
        const struct thermal_zone_params *tzp;
        struct thermal_cooling_device *cdev;
        struct thermal_zone_device *pos = NULL;
@@ -1525,6 +1525,7 @@ void thermal_zone_device_unregister(struct 
thermal_zone_device *tz)
                return;
 
        tzp = tz->tzp;
+       tz_id = tz->id;
 
        mutex_lock(&thermal_list_lock);
        list_for_each_entry(pos, &thermal_tz_list, node)
@@ -1560,14 +1561,13 @@ void thermal_zone_device_unregister(struct 
thermal_zone_device *tz)
        cancel_delayed_work_sync(&tz->poll_queue);
 
        thermal_set_governor(tz, NULL);
-
        thermal_remove_hwmon_sysfs(tz);
        ida_simple_remove(&thermal_tz_ida, tz->id);
        ida_destroy(&tz->ida);
        mutex_destroy(&tz->lock);
        device_unregister(&tz->device);
 
-       thermal_notify_tz_delete(tz->id);
+       thermal_notify_tz_delete(tz_id);
 }
 EXPORT_SYMBOL_GPL(thermal_zone_device_unregister);
 
-- 
2.27.0