linux-kernel - Re: [PATCH v2] gpio: virtuser: fix UAF in configfs release path

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Message-ID: <CAMRc=Mc3Na--W81n0DTvarDPEsHDjSMksCYSLMkUt9ewf3FVKg@mail.gmail.com>
Date: Tue, 27 Jan 2026 10:15:48 +0100
From: Bartosz Golaszewski <brgl@...nel.org>
To: Yuhao Huang <nekowong743@...il.com>
Cc: linux-gpio@...r.kernel.org, linus.walleij@...aro.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] gpio: virtuser: fix UAF in configfs release path

On Mon, Jan 26, 2026 at 5:03 AM Yuhao Huang <nekowong743@...il.com> wrote:
>
> From: Yuhao Huang <nekowong743@...il.com>
>
> The gpio-virtuser configfs release path uses guard(mutex) to protect
> the device structure. However, the device is freed before the guard
> cleanup runs, causing mutex_unlock() to operate on freed memory.
>
> Specifically, gpio_virtuser_device_config_group_release() destroys
> the mutex and frees the device while still inside the guard(mutex)
> scope. When the function returns, the guard cleanup invokes
> mutex_unlock(&dev->lock), resulting in a slab use-after-free.
>
> Limit the mutex lifetime by using a scoped_guard() only around the
> activation check, so that the lock is released before mutex_destroy()
> and kfree() are called.
>
> Fixes: 91581c4b3f29 ("gpio: virtuser: new virtual testing driver for the GPIO API")
> Signed-off-by: Yuhao Huang <nekowong743@...il.com>
> ---

I queued this but please don't send patches with In-reply-to:
referencing previous versions. Also: please use get_maintainer.pl - it
would have given you my kernel.org address.

Bartosz