watchdog: pcwd_usb: fix NULL-deref at probe

BugLink: http://bugs.launchpad.net/bugs/1694621

commit 46c319b8 upstream.

Make sure to check the number of endpoints to avoid dereferencing a
NULL-pointer should a malicious device lack endpoints.

Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Signed-off-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

drivers/watchdog/pcwd_usb.c

@@ -630,6 +630,9 @@ static int usb_pcwd_probe(struct usb_interface *interface,
 		return -ENODEV;
 	}
 
+	if (iface_desc->desc.bNumEndpoints < 1)
+		return -ENODEV;
+
 	/* check out the endpoint: it has to be Interrupt & IN */
 	endpoint = &iface_desc->endpoint[0].desc;