From: Yuhao Huang <nekowong743@gmail.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@gmail.com>
---
Changes in v2:
- Fix indentation to match kernel coding style
---
 drivers/gpio/gpio-virtuser.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/gpio/gpio-virtuser.c b/drivers/gpio/gpio-virtuser.c
index 37f2ce20f1ae7..098e67d70ffa5 100644
--- a/drivers/gpio/gpio-virtuser.c
+++ b/drivers/gpio/gpio-virtuser.c
@@ -1682,10 +1682,10 @@ static void gpio_virtuser_device_config_group_release(struct config_item *item)
 {
 	struct gpio_virtuser_device *dev = to_gpio_virtuser_device(item);
 
-	guard(mutex)(&dev->lock);
-
-	if (gpio_virtuser_device_is_live(dev))
-		gpio_virtuser_device_deactivate(dev);
+	scoped_guard(mutex, &dev->lock) {
+		if (gpio_virtuser_device_is_live(dev))
+			gpio_virtuser_device_deactivate(dev);
+	}
 
 	mutex_destroy(&dev->lock);
 	ida_free(&gpio_virtuser_ida, dev->id);
-- 
2.43.0

On Mon, 26 Jan 2026 12:03:48 +0800, Yuhao Huang wrote:
> 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.
> 
> [...]

Applied, thanks!

[1/1] gpio: virtuser: fix UAF in configfs release path
      commit: 320ae0de18e16ad6ba45f4bbc493a3d141d3b94c

Best regards,
-- 
Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>

On Mon, Jan 26, 2026 at 5:03 AM Yuhao Huang <nekowong743@gmail.com> wrote:
>
> From: Yuhao Huang <nekowong743@gmail.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@gmail.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