linux-kernel - Re: [PATCH] thermal: Fix slab-out-of-bounds in thermal_cooling_device_stats

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Date:   Tue, 17 Nov 2020 15:15:02 +0800
From:   Zhang Rui <rui.zhang@...el.com>
To:     zhuguangqing83@...il.com, daniel.lezcano@...aro.org,
        amitk@...nel.org
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        zhuguangqing@...omi.com
Subject: Re: [PATCH] thermal: Fix slab-out-of-bounds in
 thermal_cooling_device_stats_update()

On Tue, 2020-09-15 at 13:58 +0800, zhuguangqing83@...il.com wrote:
> From: zhuguangqing <zhuguangqing@...omi.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@...omi.com>

Hi, Daniel,

this patch is a similar fix as

https://patchwork.kernel.org/project/linux-pm/patch/20200408041917.2329-4-rui.zhang@intel.com/

I think we'd better take the original fix from Takashi Iwai.
And I will refresh and submit the patches that supports dynamic cooling
states later when I have time.

thanks,
rui
> ---
>  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);