usb: idmouse: fix an uninit-value in idmouse_open

In idmouse_create_image, if any ftip_command fails, it will
go to the reset label. However, this leads to the data in
bulk_in_buffer[HEADER..IMGSIZE] uninitialized. And the check
for valid image incurs an uninitialized dereference.

Fix this by moving the check before reset label since this
check only be valid if the data after bulk_in_buffer[HEADER]
has concrete data.

Note that this is found by KMSAN, so only kernel compilation
is tested.

Reported-by: syzbot+79832d33eb89fb3cd092@syzkaller.appspotmail.com
Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.com>
Link: https://lore.kernel.org/r/20220922134847.1101921-1-dzm91@hust.edu.cnSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/misc/idmouse.c

@@ -177,10 +177,6 @@ static int idmouse_create_image(struct usb_idmouse *dev)
 		bytes_read += bulk_read;
 	}
 
-	/* reset the device */
-reset:
-	ftip_command(dev, FTIP_RELEASE, 0, 0);
-
 	/* check for valid image */
 	/* right border should be black (0x00) */
 	for (bytes_read = sizeof(HEADER)-1 + WIDTH-1; bytes_read < IMGSIZE; bytes_read += WIDTH)
@@ -192,6 +188,10 @@ static int idmouse_create_image(struct usb_idmouse *dev)
 		if (dev->bulk_in_buffer[bytes_read] != 0xFF)
 			return -EAGAIN;
 
+	/* reset the device */
+reset:
+	ftip_command(dev, FTIP_RELEASE, 0, 0);
+
 	/* should be IMGSIZE == 65040 */
 	dev_dbg(&dev->interface->dev, "read %d bytes fingerprint data\n",
 		bytes_read);