USB: cypress_m8: add endpoint sanity check

commit c55aee1b upstream.

An attack using missing endpoints exists.

CVE-2016-3137
Signed-off-by: Oliver Neukum <ONeukum@suse.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/usb/serial/cypress_m8.c

@@ -489,6 +489,11 @@ static int generic_startup(struct usb_serial *serial)
 
 	dbg("%s - port %d", __func__, port->number);
 
+	if (!port->interrupt_out_urb || !port->interrupt_in_urb) {
+		dev_err(&port->dev, "required endpoint is missing\n");
+		return -ENODEV;
+	}
+
 	priv = kzalloc(sizeof(struct cypress_private), GFP_KERNEL);
 	if (!priv)
 		return -ENOMEM;
@@ -658,12 +663,6 @@ static int cypress_open(struct tty_struct *tty, struct usb_serial_port *port)
 		cypress_set_termios(tty, port, &priv->tmp_termios);
 
 	/* setup the port and start reading from the device */
-	if (!port->interrupt_in_urb) {
-		dev_err(&port->dev, "%s - interrupt_in_urb is empty!\n",
-			__func__);
-		return -1;
-	}
-
 	usb_fill_int_urb(port->interrupt_in_urb, serial->dev,
 		usb_rcvintpipe(serial->dev, port->interrupt_in_endpointAddress),
 		port->interrupt_in_urb->transfer_buffer,