[v1] gpio: virtuser: fix UAF in configfs release path

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

Posted by Yuhao Huang 1 week, 6 days ago

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

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

Posted by kernel test robot 1 week, 6 days ago

Hi Yuhao,

kernel test robot noticed the following build warnings:

[auto build test WARNING on brgl/gpio/for-next]
[also build test WARNING on linus/master v6.19-rc6 next-20260123]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Yuhao-Huang/gpio-virtuser-fix-UAF-in-configfs-release-path/20260125-002359
base:   https://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux.git gpio/for-next
patch link:    https://lore.kernel.org/r/20260124162111.3945666-1-nekowong743%40gmail.com
patch subject: [PATCH] gpio: virtuser: fix UAF in configfs release path
config: m68k-randconfig-r073-20260125 (https://download.01.org/0day-ci/archive/20260125/202601251126.ywFiWrat-lkp@intel.com/config)
compiler: m68k-linux-gcc (GCC) 11.5.0
smatch version: v0.5.0-8994-gd50c5a4c

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202601251126.ywFiWrat-lkp@intel.com/

smatch warnings:
drivers/gpio/gpio-virtuser.c:1685 gpio_virtuser_device_config_group_release() warn: inconsistent indenting

vim +1685 drivers/gpio/gpio-virtuser.c

  1680	
  1681	static void gpio_virtuser_device_config_group_release(struct config_item *item)
  1682	{
  1683		struct gpio_virtuser_device *dev = to_gpio_virtuser_device(item);
  1684	
> 1685	    scoped_guard(mutex, &dev->lock) {
  1686	        if (gpio_virtuser_device_is_live(dev))
  1687	            gpio_virtuser_device_deactivate(dev);
  1688	    }
  1689	
  1690		mutex_destroy(&dev->lock);
  1691		ida_free(&gpio_virtuser_ida, dev->id);
  1692		kfree(dev);
  1693	}
  1694	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

[PATCH v2] gpio: virtuser: fix UAF in configfs release path

Posted by Yuhao Huang 1 week, 5 days ago

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

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

Posted by Bartosz Golaszewski 1 week, 3 days ago

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>

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

Posted by Bartosz Golaszewski 1 week, 3 days ago

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