Re: [PATCH] Input: wacom_w8001 - avoid double release of pen input device

[Peter Hutterer <peter.hutterer@who-t.net>]

On Thu, Apr 30, 2026 at 03:13:11PM +0800, Guangshuo Li wrote:
> When registering the touch input device fails after the pen input device
> has already been registered, w8001_connect() jumps to fail4 and
> unregisters w8001->pen_dev.  It then falls through to fail1 where
> input_dev_pen is passed to input_free_device().
> 
> Once input_register_device() has succeeded, the device must be released
> with input_unregister_device(), and input_free_device() must not be used
> on the same object afterwards.  Since input_dev_pen still aliases
> w8001->pen_dev, this can result in a use-after-free or kref underflow.
> 
> Clear the local and container aliases after unregistering the pen device
> so that the common cleanup path does not try to free it again.
> 
> This issue was found by a static analysis tool I am developing.
> 
> Fixes: e0361b70175f0 ("Input: wacom_w8001 - split the touch and pen devices into two devices")
> Signed-off-by: Guangshuo Li <lgs201920130244@gmail.com>

Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>

thanks

Cheers,
  Peter

> ---
>  drivers/input/touchscreen/wacom_w8001.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/input/touchscreen/wacom_w8001.c b/drivers/input/touchscreen/wacom_w8001.c
> index 45930d731873..a3b283c59cdd 100644
> --- a/drivers/input/touchscreen/wacom_w8001.c
> +++ b/drivers/input/touchscreen/wacom_w8001.c
> @@ -665,8 +665,11 @@ static int w8001_connect(struct serio *serio, struct serio_driver *drv)
>  	return 0;
>  
>  fail4:
> -	if (w8001->pen_dev)
> +	if (w8001->pen_dev) {
>  		input_unregister_device(w8001->pen_dev);
> +		input_dev_pen = NULL;
> +		w8001->pen_dev = NULL;
> +	}
>  fail3:
>  	serio_close(serio);
>  fail2:
> -- 
> 2.43.0
>