[PATCH 3.2 86/87] [media] usbvision fix overflow of interfaces array

[Ben Hutchings]

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

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

From: Oliver Neukum <oneukum@xxxxxxxx>

commit 588afcc1c0e45358159090d95bf7b246fb67565f upstream.

This fixes the crash reported in:
http://seclists.org/bugtraq/2015/Oct/35
The interface number needs a sanity check.

Signed-off-by: Oliver Neukum <oneukum@xxxxxxxx>
Cc: Vladis Dronov <vdronov@xxxxxxxxxx>
Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxx>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/media/video/usbvision/usbvision-video.c | 7 +++++++
 1 file changed, 7 insertions(+)

--- a/drivers/media/video/usbvision/usbvision-video.c
+++ b/drivers/media/video/usbvision/usbvision-video.c
@@ -1502,6 +1502,13 @@ static int __devinit usbvision_probe(str
 	printk(KERN_INFO "%s: %s found\n", __func__,
 				usbvision_device_data[model].model_string);
 
+	/*
+	 * this is a security check.
+	 * an exploit using an incorrect bInterfaceNumber is known
+	 */
+	if (ifnum >= USB_MAXINTERFACES || !dev->actconfig->interface[ifnum])
+		return -ENODEV;
+
 	if (usbvision_device_data[model].interface >= 0)
 		interface = &dev->actconfig->interface[usbvision_device_data[model].interface]->altsetting[0];
 	else