usbvision: fix crash on detecting device with invalid configuration

commit fa52bd50 upstream.

The usbvision driver crashes when a specially crafted usb device with invalid
number of interfaces or endpoints is detected. This fix adds checks that the
device has proper configuration expected by the driver.
Reported-by: Ralf Spenneberg <ralf@spenneberg.net>
Signed-off-by: Vladis Dronov <vdronov@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
[bwh: Backport to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/media/video/usbvision/usbvision-video.c

@@ -1511,9 +1511,23 @@ static int __devinit usbvision_probe(struct usb_interface *intf,
 
 	if (usbvision_device_data[model].interface >= 0)
 		interface = &dev->actconfig->interface[usbvision_device_data[model].interface]->altsetting[0];
-	else
+	else if (ifnum < dev->actconfig->desc.bNumInterfaces)
 		interface = &dev->actconfig->interface[ifnum]->altsetting[0];
+	else {
+		dev_err(&intf->dev, "interface %d is invalid, max is %d\n",
+		    ifnum, dev->actconfig->desc.bNumInterfaces - 1);
+		ret = -ENODEV;
+		goto err_usb;
+	}
+
+	if (interface->desc.bNumEndpoints < 2) {
+		dev_err(&intf->dev, "interface %d has %d endpoints, but must"
+		    " have minimum 2\n", ifnum, interface->desc.bNumEndpoints);
+		ret = -ENODEV;
+		goto err_usb;
+	}
 	endpoint = &interface->endpoint[1].desc;
+
 	if (!usb_endpoint_xfer_isoc(endpoint)) {
 		dev_err(&intf->dev, "%s: interface %d. has non-ISO endpoint!\n",
 		    __func__, ifnum);