[PATCH 4.9 103/164] [media] zr364xx: enforce minimum size when reading header

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Alyssa Milburn <amilburn@xxxxxxxx>

commit ee0fe833d96793853335844b6d99fb76bd12cbeb 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@xxxxxxxx>
Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/media/usb/zr364xx/zr364xx.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/drivers/media/usb/zr364xx/zr364xx.c
+++ b/drivers/media/usb/zr364xx/zr364xx.c
@@ -604,6 +604,14 @@ static int zr364xx_read_video_callback(s
 	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;