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From:   zhuguangqing83@gmail.com
To:     rui.zhang@intel.com, daniel.lezcano@linaro.org, amitk@kernel.org
Cc:     linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org,
        zhuguangqing@xiaomi.com
Subject: [PATCH] thermal: Fix slab-out-of-bounds in thermal_cooling_device_stats_update()
Date:   Tue, 15 Sep 2020 13:58:37 +0800
Message-Id: <20200915055837.498-1-zhuguangqing83@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: zhuguangqing <zhuguangqing@xiaomi.com>

In function thermal_cooling_device_stats_update(), if the input parameter
new_state is greater or equal to stats->max_states, then it will cause
slab-out-of-bounds error when execute the code as follows:
stats->trans_table[stats->state * stats->max_states + new_state]++;

Two functions call the function thermal_cooling_device_stats_update().
1. cur_state_store()
2. thermal_cdev_set_cur_state()
Both of the two functions call cdev->ops->set_cur_state(cdev, state)
before thermal_cooling_device_stats_update(), if the return value is
not 0, then thermal_cooling_device_stats_update() will not be called.
So if all cdev->ops->set_cur_state(cdev, state) check validity of the
parameter state, then it's ok. Unfortunately, it's not now.

We have two methods to avoid the slab-out-of-bounds error in
thermal_cooling_device_stats_update().
1. Check the validity of the parameter state in all
cdev->ops->set_cur_state(cdev, state).
2. Check the validity of the parameter state in
thermal_cooling_device_stats_update().

Use method 2 in this patch. Because the modification is simple and
resolve the problem in the scope of "#ifdef CONFIG_THERMAL_STATISTICS".

Signed-off-by: zhuguangqing <zhuguangqing@xiaomi.com>
---
 drivers/thermal/thermal_sysfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c
index 8c231219e15d..9c49f744d79d 100644
--- a/drivers/thermal/thermal_sysfs.c
+++ b/drivers/thermal/thermal_sysfs.c
@@ -756,7 +756,7 @@ void thermal_cooling_device_stats_update(struct thermal_cooling_device *cdev,
 
 	spin_lock(&stats->lock);
 
-	if (stats->state == new_state)
+	if (stats->state == new_state || new_state >= stats->max_states)
 		goto unlock;
 
 	update_time_in_state(stats);
-- 
2.17.1