[PATCH 3.16.y-ckt 001/129] [media] usbvision fix overflow of interfaces array

[Luis Henriques]

3.16.7-ckt25 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Oliver Neukum <oneukum at suse.com>

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 at suse.com>
Cc: Vladis Dronov <vdronov at redhat.com>
Signed-off-by: Hans Verkuil <hans.verkuil at cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab at osg.samsung.com>
Cc: Moritz Muehlenhoff <jmm at inutil.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/media/usb/usbvision/usbvision-video.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/media/usb/usbvision/usbvision-video.c b/drivers/media/usb/usbvision/usbvision-video.c
index 68bc9615660e..01d0dd99bb24 100644
--- a/drivers/media/usb/usbvision/usbvision-video.c
+++ b/drivers/media/usb/usbvision/usbvision-video.c
@@ -1536,6 +1536,13 @@ static int usbvision_probe(struct usb_interface *intf,
 	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