[PATCH v2] thermal: core: Fix use-after-free in thermal_zone_device_unregister()

[PATCH v2] 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 <digetx@gmail.com>
---

Changelog:

v2: - Don't touch lines unrelated to the actual fix.

 drivers/thermal/thermal_core.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index 72bf159bcecc..a6616e530a84 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)
@@ -1567,7 +1568,7 @@ void thermal_zone_device_unregister(struct thermal_zone_device *tz)
 	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

Re: [PATCH v2] thermal: core: Fix use-after-free in thermal_zone_device_unregister()

[Daniel Lezcano]

On 18/08/2020 01:58, Dmitry Osipenko wrote:
> 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 <digetx@gmail.com>
> ---

Applied, thanks !


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