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Subject[PATCH] thermal: Fix slab-out-of-bounds in thermal_cooling_device_stats_update()
Date
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
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