[PATCH 3.2 18/59] [media] usbvision: fix NULL-deref at probe

[Ben Hutchings]

3.2.92-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Johan Hovold <johan@xxxxxxxxxx>

commit eacb975b48272f54532b62f515a3cf7eefa35123 upstream.

Make sure to check the number of endpoints to avoid dereferencing a
NULL-pointer or accessing memory beyond the endpoint array should a
malicious device lack the expected endpoints.

Fixes: 2a9f8b5d25be ("V4L/DVB (5206): Usbvision: set alternate interface
modification")

Cc: Thierry MERLE <thierry.merle@xxxxxxx>
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxxx>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/media/video/usbvision/usbvision-video.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

--- a/drivers/media/video/usbvision/usbvision-video.c
+++ b/drivers/media/video/usbvision/usbvision-video.c
@@ -1564,7 +1564,14 @@ static int __devinit usbvision_probe(str
 	}
 
 	for (i = 0; i < usbvision->num_alt; i++) {
-		u16 tmp = le16_to_cpu(uif->altsetting[i].endpoint[1].desc.
+		u16 tmp;
+
+		if (uif->altsetting[i].desc.bNumEndpoints < 2) {
+			ret = -ENODEV;
+			goto err_pkt;
+		}
+
+		tmp = le16_to_cpu(uif->altsetting[i].endpoint[1].desc.
 				      wMaxPacketSize);
 		usbvision->alt_max_pkt_size[i] =
 			(tmp & 0x07ff) * (((tmp & 0x1800) >> 11) + 1);