media: uvcvideo: Fix error path in control parsing failure

When parsing the UVC control descriptors fails, the error path tries to
cleanup a media device that hasn't been initialised, potentially
resulting in a crash. Fix this by initialising the media device before
the error handling path can be reached.

Fixes: 5a254d7 ("[media] uvcvideo: Register a v4l2_device")
Reported-by: syzbot+c86454eb3af9e8a4da20@syzkaller.appspotmail.com
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/usb/uvc/uvc_driver.c

@@ -2151,6 +2151,20 @@ static int uvc_probe(struct usb_interface *intf,
 			   sizeof(dev->name) - len);
 	}
 
+	/* Initialize the media device. */
+#ifdef CONFIG_MEDIA_CONTROLLER
+	dev->mdev.dev = &intf->dev;
+	strscpy(dev->mdev.model, dev->name, sizeof(dev->mdev.model));
+	if (udev->serial)
+		strscpy(dev->mdev.serial, udev->serial,
+			sizeof(dev->mdev.serial));
+	usb_make_path(udev, dev->mdev.bus_info, sizeof(dev->mdev.bus_info));
+	dev->mdev.hw_revision = le16_to_cpu(udev->descriptor.bcdDevice);
+	media_device_init(&dev->mdev);
+
+	dev->vdev.mdev = &dev->mdev;
+#endif
+
 	/* Parse the Video Class control descriptor. */
 	if (uvc_parse_control(dev) < 0) {
 		uvc_trace(UVC_TRACE_PROBE, "Unable to parse UVC "
@@ -2171,19 +2185,7 @@ static int uvc_probe(struct usb_interface *intf,
 			"linux-uvc-devel mailing list.\n");
 	}
 
-	/* Initialize the media device and register the V4L2 device. */
-#ifdef CONFIG_MEDIA_CONTROLLER
-	dev->mdev.dev = &intf->dev;
-	strscpy(dev->mdev.model, dev->name, sizeof(dev->mdev.model));
-	if (udev->serial)
-		strscpy(dev->mdev.serial, udev->serial,
-			sizeof(dev->mdev.serial));
-	usb_make_path(udev, dev->mdev.bus_info, sizeof(dev->mdev.bus_info));
-	dev->mdev.hw_revision = le16_to_cpu(udev->descriptor.bcdDevice);
-	media_device_init(&dev->mdev);
-
-	dev->vdev.mdev = &dev->mdev;
-#endif
+	/* Register the V4L2 device. */
 	if (v4l2_device_register(&intf->dev, &dev->vdev) < 0)
 		goto error;