linux-kernel - Re: [PATCH -next] thermal/drivers/thermal_hwmon: Fix a kernel NULL pointer dereference

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Message-ID: <08aee7fe-eddc-7841-2539-16ae43fd8d66@linaro.org>
Date:   Wed, 29 Mar 2023 11:57:32 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Zhang Rui <rui.zhang@...el.com>, linux-pm@...r.kernel.org,
        rafael.j.wysocki@...el.com
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] thermal/drivers/thermal_hwmon: Fix a kernel NULL
 pointer dereference

On 29/03/2023 11:00, Zhang Rui wrote:
> When the hwmon device node of a thermal zone device is not found,
> using hwmon->device causes a kernel NULL pointer dereference.
> 
> Reported-by: Preble Adam C <adam.c.preble@...el.com>
> Signed-off-by: Zhang Rui <rui.zhang@...el.com>
> ---
> Fixes: dec07d399cc8 ("thermal: Don't use 'device' internal thermal zone structure field")
> dec07d399cc8 is a commit in the linux-next branch of linux-pm repo.
> I'm not sure if the Fix tag applies to such commit or not.

Actually it reverts the work done to encapsulate the thermal zone device 
structure.

> ---
>   drivers/thermal/thermal_hwmon.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/thermal/thermal_hwmon.c b/drivers/thermal/thermal_hwmon.c
> index c59db17dddd6..261743f461be 100644
> --- a/drivers/thermal/thermal_hwmon.c
> +++ b/drivers/thermal/thermal_hwmon.c
> @@ -229,7 +229,7 @@ void thermal_remove_hwmon_sysfs(struct thermal_zone_device *tz)
>   	hwmon = thermal_hwmon_lookup_by_type(tz);
>   	if (unlikely(!hwmon)) {
>   		/* Should never happen... */
> -		dev_dbg(hwmon->device, "hwmon device lookup failed!\n");
> +		dev_dbg(&tz->device, "hwmon device lookup failed!\n");

As it 'Should never happen', I would replace that by:

	if (WARN_ON(!hwmon))
		/* Should never happen... */
		return;



>   		return;
>   	}
>   

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