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

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Date:   Wed, 29 Mar 2023 18:18:31 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Zhang Rui <rui.zhang@...el.com>, linux-pm@...r.kernel.org,
        rafael.j.wysocki@...el.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] thermal/drivers/thermal_hwmon: Fix a kernel NULL
 pointer dereference

On 29/03/2023 18:03, Rafael J. Wysocki wrote:
> On Wed, Mar 29, 2023 at 5:59 PM Daniel Lezcano
> <daniel.lezcano@...aro.org> wrote:
>>
>> On 29/03/2023 16:38, Rafael J. Wysocki wrote:
>>> On Wed, Mar 29, 2023 at 4:16 PM Daniel Lezcano
>>> <daniel.lezcano@...aro.org> wrote:
>>>>
>>>> On 29/03/2023 14:06, Rafael J. Wysocki wrote:
>>>>> On Wed, Mar 29, 2023 at 11:57 AM Daniel Lezcano
>>>>> <daniel.lezcano@...aro.org> wrote:
>>>>>>
>>>>>> 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.
>>>>>
>>>>> So maybe instead of the wholesale switch to using "driver-specific"
>>>>> device pointers for printing messages, something like
>>>>> thermal_zone_debug/info/warn/error() taking a thermal zone pointer as
>>>>> the first argument can be defined?
>>>>>
>>>>> At least this particular bug could be avoided this way.
>>>>
>>>> Actually we previously said the thermal_hwmon can be considered as part
>>>> of the thermal core code, so we can keep using tz->device.
>>>>
>>>> I'll drop this change from the series.
>>>
>>> But it's there in my thermal branch already.
>>>
>>> Do you want to revert the thermal_hwmon.c part of commit dec07d399cc8?
>>
>> Oh, right. Fair enough.
>>
>> I think Rui's patch is fine then.
> 
> I guess you mean the $subject one, that is:
> 
> https://patchwork.kernel.org/project/linux-pm/patch/20230329090055.7537-1-rui.zhang@intel.com

Correct

> What about the message printed when temp is NULL.  Should the original
> form of it be restored too?

Yes, you are right, for the sake of consistency we should restore also 
this one.



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