usbtest_probe(struct usb_interface *intf, const struct usb_device_id *id)
{
	struct usb_device	*udev;
	struct usbtest_dev	*dev;
	struct usbtest_info	*info;
	char			*rtest, *wtest;
	char			*irtest, *iwtest;
	char			*intrtest, *intwtest;

	udev = interface_to_usbdev(intf);

#ifdef	GENERIC
	/* specify devices by module parameters? */
	if (id->match_flags == 0) {
		/* vendor match required, product match optional */
		if (!vendor || le16_to_cpu(udev->descriptor.idVendor) != (u16)vendor)
			return -ENODEV;
		if (product && le16_to_cpu(udev->descriptor.idProduct) != (u16)product)
			return -ENODEV;
		dev_info(&intf->dev, "matched module params, "
					"vend=0x%04x prod=0x%04x\n",
				le16_to_cpu(udev->descriptor.idVendor),
				le16_to_cpu(udev->descriptor.idProduct));
	}
#endif

	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
	if (!dev)
		return -ENOMEM;
	info = (struct usbtest_info *) id->driver_info;
	dev->info = info;
	mutex_init(&dev->lock);

	dev->intf = intf;

	/* cacheline-aligned scratch for i/o */
	dev->buf = kmalloc(TBUF_SIZE, GFP_KERNEL);
	if (dev->buf == NULL) {
		kfree(dev);
		return -ENOMEM;
	}

	/* NOTE this doesn't yet test the handful of difference that are
	 * visible with high speed interrupts:  bigger maxpacket (1K) and
	 * "high bandwidth" modes (up to 3 packets/uframe).
	 */
	rtest = wtest = "";
	irtest = iwtest = "";
	intrtest = intwtest = "";
	if (force_interrupt || udev->speed == USB_SPEED_LOW) {
		if (info->ep_in) {
			dev->in_pipe = usb_rcvintpipe(udev, info->ep_in);
			rtest = " intr-in";
		}
		if (info->ep_out) {
			dev->out_pipe = usb_sndintpipe(udev, info->ep_out);
			wtest = " intr-out";
		}
	} else {
		if (override_alt >= 0 || info->autoconf) {
			int status;

			status = get_endpoints(dev, intf);
			if (status < 0) {
				WARNING(dev, "couldn't get endpoints, %d\n",
						status);
				kfree(dev->buf);
				kfree(dev);
				return status;
			}
			/* may find bulk or ISO pipes */
		} else {
			if (info->ep_in)
				dev->in_pipe = usb_rcvbulkpipe(udev,
							info->ep_in);
			if (info->ep_out)
				dev->out_pipe = usb_sndbulkpipe(udev,
							info->ep_out);
		}
		if (dev->in_pipe)
			rtest = " bulk-in";
		if (dev->out_pipe)
			wtest = " bulk-out";
		if (dev->in_iso_pipe)
			irtest = " iso-in";
		if (dev->out_iso_pipe)
			iwtest = " iso-out";
		if (dev->in_int_pipe)
			intrtest = " int-in";
		if (dev->out_int_pipe)
			intwtest = " int-out";
	}

	usb_set_intfdata(intf, dev);
	dev_info(&intf->dev, "%s\n", info->name);
	dev_info(&intf->dev, "%s {control%s%s%s%s%s%s%s} tests%s\n",
			usb_speed_string(udev->speed),
			info->ctrl_out ? " in/out" : "",
			rtest, wtest,
			irtest, iwtest,
			intrtest, intwtest,
			info->alt >= 0 ? " (+alt)" : "");
	return 0;
}

The product dereferences a pointer that it expects to be valid but is NULL.