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

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Message-ID: <aQCg-xZ_kAemfgZQ@smile.fi.intel.com>
Date: Tue, 28 Oct 2025 12:54:51 +0200
From: Andy Shevchenko <andriy.shevchenko@...el.com>
To: Hans de Goede <hansg@...nel.org>
Cc: Dan Scally <dan.scally@...asonboard.com>,
	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

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:
> >>>
> >>> 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.

Hmm... I probably missed that, but I failed to see this. Any pointers?

> 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.

-- 
With Best Regards,
Andy Shevchenko