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

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Message-ID: <7898408e-1b33-4f22-84d2-12bcd6254402@kernel.org>
Date: Tue, 28 Oct 2025 11:38:00 +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 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:
>>>
>>> regulator_unregister() already frees the associated GPIO device. On
>>> ThinkPad X9 (Lunar Lake), this causes a double free issue that leads to
>>> random failures when other drivers (typically Intel THC) attempt to
>>> allocate interrupts. The root cause is that the reference count of the
>>> pinctrl_intel_platform module unexpectedly drops to zero when this
>>> driver defers its probe.
>>>
>>> This behavior can also be reproduced by unloading the module directly.
>>>
>>> Fix the issue by removing the redundant release of the GPIO device
>>> during regulator unregistration.
>>>
>>> Fixes: 1e5d088a52c2 ("platform/x86: int3472: Stop using devm_gpiod_get()")
> 
>> 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. Only when passed as platform-data as we do here does
this layering violation occur.

I do believe that a transfer of ownership ad done here is ok for
the platform-data special case.

Regards,

Hans