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);