Input: aiptek - fix endpoint sanity check

The driver was checking the number of endpoints of the first alternate
setting instead of the current one, something which could lead to the
driver binding to an invalid interface.

This in turn could cause the driver to misbehave or trigger a WARN() in
usb_submit_urb() that kernels with panic_on_warn set would choke on.

Fixes: 8e20cf2b ("Input: aiptek - fix crash on detecting device without endpoints")
Signed-off-by: Johan Hovold <johan@kernel.org>
Acked-by: Vladis Dronov <vdronov@redhat.com>
Link: https://lore.kernel.org/r/20191210113737.4016-3-johan@kernel.orgSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/tablet/aiptek.c

@@ -1802,14 +1802,14 @@ aiptek_probe(struct usb_interface *intf, const struct usb_device_id *id)
 	input_set_abs_params(inputdev, ABS_WHEEL, AIPTEK_WHEEL_MIN, AIPTEK_WHEEL_MAX - 1, 0, 0);
 
 	/* Verify that a device really has an endpoint */
-	if (intf->altsetting[0].desc.bNumEndpoints < 1) {
+	if (intf->cur_altsetting->desc.bNumEndpoints < 1) {
 		dev_err(&intf->dev,
 			"interface has %d endpoints, but must have minimum 1\n",
-			intf->altsetting[0].desc.bNumEndpoints);
+			intf->cur_altsetting->desc.bNumEndpoints);
 		err = -EINVAL;
 		goto fail3;
 	}
-	endpoint = &intf->altsetting[0].endpoint[0].desc;
+	endpoint = &intf->cur_altsetting->endpoint[0].desc;
 
 	/* Go set up our URB, which is called when the tablet receives
 	 * input.