[PATCH] gpio: virtuser: fix UAF in configfs release path

[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>
---
 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 37f2ce20f..6de5dcc97 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