zr364xx: enforce minimum size when reading header

commit ee0fe833 upstream.

This code copies actual_length-128 bytes from the header, which will
underflow if the received buffer is too small.
Signed-off-by: Alyssa Milburn <amilburn@zall.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/media/video/zr364xx.c

@@ -611,6 +611,14 @@ static int zr364xx_read_video_callback(struct zr364xx_camera *cam,
 	ptr = pdest = frm->lpvbits;
 
 	if (frm->ulState == ZR364XX_READ_IDLE) {
+		if (purb->actual_length < 128) {
+			/* header incomplete */
+			dev_info(&cam->udev->dev,
+				 "%s: buffer (%d bytes) too small to hold jpeg header. Discarding.\n",
+				 __func__, purb->actual_length);
+			return -EINVAL;
+		}
+
 		frm->ulState = ZR364XX_READ_FRAME;
 		frm->cur_size = 0;