USB: digi_acceleport: do sanity checking for the number of ports

The driver can be crashed with devices that expose crafted descriptors
with too few endpoints.

See: http://seclists.org/bugtraq/2016/Mar/61

Signed-off-by: Oliver Neukum <ONeukum@suse.com>
[johan: fix OOB endpoint check and add error messages ]
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/serial/digi_acceleport.c

@@ -1251,8 +1251,27 @@ static int digi_port_init(struct usb_serial_port *port, unsigned port_num)
 
 static int digi_startup(struct usb_serial *serial)
 {
+	struct device *dev = &serial->interface->dev;
 	struct digi_serial *serial_priv;
 	int ret;
+	int i;
+
+	/* check whether the device has the expected number of endpoints */
+	if (serial->num_port_pointers < serial->type->num_ports + 1) {
+		dev_err(dev, "OOB endpoints missing\n");
+		return -ENODEV;
+	}
+
+	for (i = 0; i < serial->type->num_ports + 1 ; i++) {
+		if (!serial->port[i]->read_urb) {
+			dev_err(dev, "bulk-in endpoint missing\n");
+			return -ENODEV;
+		}
+		if (!serial->port[i]->write_urb) {
+			dev_err(dev, "bulk-out endpoint missing\n");
+			return -ENODEV;
+		}
+	}
 
 	serial_priv = kzalloc(sizeof(*serial_priv), GFP_KERNEL);
 	if (!serial_priv)