Re: [syzbot] [media?] [usb?] KASAN: slab-use-after-free Read in v4l2_open

[Edward Adam Davis]

#syz test

diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
index 6ce623a1245a..0639315f9611 100644
--- a/drivers/media/v4l2-core/v4l2-dev.c
+++ b/drivers/media/v4l2-core/v4l2-dev.c
@@ -423,7 +423,6 @@ static int v4l2_open(struct inode *inode, struct file *filp)
 	}
 	/* and increase the device refcount */
 	video_get(vdev);
-	mutex_unlock(&videodev_lock);
 
 	if (!video_is_registered(vdev)) {
 		ret = -ENODEV;
@@ -448,6 +447,7 @@ static int v4l2_open(struct inode *inode, struct file *filp)
 	/* decrease the refcount in case of an error */
 	if (ret)
 		video_put(vdev);
+	mutex_unlock(&videodev_lock);
 	return ret;
 }