linux-kernel - Re: [PATCH] platform/x86: int3472: Fix double free of GPIO device during unregister

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Message-ID: <492c05bf-bf0f-4cca-af3b-121fdffd05e8@kernel.org>
Date: Tue, 28 Oct 2025 15:36:56 +0100
From: Hans de Goede <hansg@...nel.org>
To: Andy Shevchenko <andriy.shevchenko@...el.com>,
 Dan Scally <dan.scally@...asonboard.com>
Cc: Qiu Wenbo <qiuwenbo@...me.org>, Daniel Scally <djrscally@...il.com>,
 Qiu Wenbo <qiuwenbo@...insec.com.cn>, platform-driver-x86@...r.kernel.org,
 linux-kernel@...r.kernel.org, Ilpo Järvinen
 <ilpo.jarvinen@...ux.intel.com>, Sakari Ailus
 <sakari.ailus@...ux.intel.com>, Andy Shevchenko <andy@...nel.org>
Subject: Re: [PATCH] platform/x86: int3472: Fix double free of GPIO device
 during unregister

Hi,

On 28-Oct-25 12:38 PM, Andy Shevchenko wrote:
> On Tue, Oct 28, 2025 at 11:09:12AM +0000, Dan Scally wrote:
>> On 28/10/2025 10:54, Andy Shevchenko wrote:
>>> On Tue, Oct 28, 2025 at 11:38:00AM +0100, Hans de Goede wrote:
>>>> On 28-Oct-25 11:02 AM, Andy Shevchenko wrote:
>>>>> On Tue, Oct 28, 2025 at 08:55:07AM +0000, Dan Scally wrote:
>>>>>> On 24/10/2025 06:05, Qiu Wenbo wrote:
> 
> ...
> 
>>>>>> However the Fixes tag I wonder about; devm_gpiod_get() will also result in a
>>>>>> call to gpiod_put() when the module is unloaded; doesn't that mean that the
>>>>>> same issue  will occur before that commit?
>>>>>
>>>>> Actually a good question! To me sounds like it's a bug(?) in regulator code.
>>>>> It must not release resources it didn't acquire. This sounds like a clear
>>>>> layering violation.
>>>>
>>>> I think the problem is that when it comes from devicetree it is acquired
>>>> by the regulator core.
>>>
>>> Hmm... I probably missed that, but I failed to see this. Any pointers?
>>
>> They can come through the struct regulator_desc.of_parse_cb(), which is called in
>> regulator_of_init_data(), from regulator_register(). For example: https://elixir.bootlin.com/linux/v6.17.5/source/drivers/power/supply/mt6370-charger.c#L234>
> 
> Ah, thank you, Dan, for the pointers. Indeed, that's how it's done. Hmm, still
> why can't we let the regulator consumer to decide when to clean the resource?
> I think this is an attempt to have a refcounting against shared GPIO resource
> and it should be done in the GPIOLIB (if not yet). In regulator that put
> call should probably be conditional (based on the source of GPIO request).

Fixing this sounds like a somewhat big undertaking. In the mean time
I think we should move forward with this patch to fix the immediate
issue with the double free.

Regards,

Hans