[PATCH -next] media: adv7604: fix possible use-after-free in adv76xx_remove()

[Yang Yingliang]

This driver's remove path calls cancel_delayed_work(). However, that
function does not wait until the work function finishes. This means
that the callback function may still be running after the driver's
remove function has finished, which would result in a use-after-free.

Fix by calling cancel_delayed_work_sync(), which ensures that
the work is properly cancelled, no longer running, and unable
to re-schedule itself.

Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
Signed-off-by: Yang Yingliang <yangyingliang@xxxxxxxxxx>
---
 drivers/media/i2c/adv7604.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/i2c/adv7604.c b/drivers/media/i2c/adv7604.c
index 18184297e2f0..9cf6de66ae25 100644
--- a/drivers/media/i2c/adv7604.c
+++ b/drivers/media/i2c/adv7604.c
@@ -3618,7 +3618,7 @@ static int adv76xx_remove(struct i2c_client *client)
 	io_write(sd, 0x6e, 0);
 	io_write(sd, 0x73, 0);
 
-	cancel_delayed_work(&state->delayed_work_enable_hotplug);
+	cancel_delayed_work_sync(&state->delayed_work_enable_hotplug);
 	v4l2_async_unregister_subdev(sd);
 	media_entity_cleanup(&sd->entity);
 	adv76xx_unregister_clients(to_state(sd));
-- 
2.25.1