linux-kernel - [PATCH v1] thermal: core: Fix use-after-free in thermal_zone_device

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Date:   Tue, 18 Aug 2020 02:48:33 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Zhang Rui <rui.zhang@...el.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Amit Kucheria <amitk@...nel.org>
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v1] thermal: core: Fix use-after-free in thermal_zone_device_unregister()

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@...il.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