Re: [PATCH v3] ACPI: video: Fix use-after-free in acpi_video_switch_brightness()

[Hans de Goede <hansg@kernel.org>]

Hi,

On 22-Oct-25 10:07 PM, Yuhao Jiang wrote:
> The switch_brightness_work delayed work accesses device->brightness
> and device->backlight, which are freed by
> acpi_video_dev_unregister_backlight() during device removal.
> 
> If the work executes after acpi_video_bus_unregister_backlight()
> frees these resources, it causes a use-after-free when
> acpi_video_switch_brightness() dereferences device->brightness or
> device->backlight.
> 
> Fix this by calling cancel_delayed_work_sync() for each device's
> switch_brightness_work in acpi_video_bus_remove_notify_handler()
> after removing the notify handler that queues the work. This ensures
> the work completes before the memory is freed.
> 
> Fixes: 8ab58e8e7e097 ("ACPI / video: Fix backlight taking 2 steps on a brightness up/down keypress")
> Cc: stable@vger.kernel.org
> Signed-off-by: Yuhao Jiang <danisjiang@gmail.com>
> ---
> Changes in v3:
> - Move cancel_delayed_work_sync() to acpi_video_bus_remove_notify_handler()
>   instead of acpi_video_bus_unregister_backlight() for better logic placement
> - Link to v2: https://lore.kernel.org/all/20251022042514.2167599-1-danisjiang@gmail.com/

Thanks, patch looks good to me:

Reviewed-by: Hans de Goede <hansg@kernel.org>

Regards,

Hans



> ---
>  drivers/acpi/acpi_video.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c
> index 103f29661576..be8e7e18abca 100644
> --- a/drivers/acpi/acpi_video.c
> +++ b/drivers/acpi/acpi_video.c
> @@ -1959,8 +1959,10 @@ static void acpi_video_bus_remove_notify_handler(struct acpi_video_bus *video)
>  	struct acpi_video_device *dev;
>  
>  	mutex_lock(&video->device_list_lock);
> -	list_for_each_entry(dev, &video->video_device_list, entry)
> +	list_for_each_entry(dev, &video->video_device_list, entry) {
>  		acpi_video_dev_remove_notify_handler(dev);
> +		cancel_delayed_work_sync(&dev->switch_brightness_work);
> +	}
>  	mutex_unlock(&video->device_list_lock);
>  
>  	acpi_video_bus_stop_devices(video);