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

[Dan Scally]

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:
> > > > > 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?

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>
> > 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.