Input: aiptek - fix crash on detecting device without endpoints

commit 8e20cf2b upstream.

The aiptek driver crashes in aiptek_probe() when a specially crafted USB
device without endpoints is detected. This fix adds a check that the device
has proper configuration expected by the driver. Also an error return value
is changed to more matching one in one of the error paths.
Reported-by: Ralf Spenneberg <ralf@spenneberg.net>
Signed-off-by: Vladis Dronov <vdronov@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/input/tablet/aiptek.c

@@ -1810,6 +1810,14 @@ aiptek_probe(struct usb_interface *intf, const struct usb_device_id *id)
 	input_set_abs_params(inputdev, ABS_TILT_Y, AIPTEK_TILT_MIN, AIPTEK_TILT_MAX, 0, 0);
 	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) {
+		dev_err(&intf->dev,
+			"interface has %d endpoints, but must have minimum 1\n",
+			intf->altsetting[0].desc.bNumEndpoints);
+		err = -EINVAL;
+		goto fail3;
+	}
 	endpoint = &intf->altsetting[0].endpoint[0].desc;
 
 	/* Go set up our URB, which is called when the tablet receives
@@ -1852,6 +1860,7 @@ aiptek_probe(struct usb_interface *intf, const struct usb_device_id *id)
 	if (i == ARRAY_SIZE(speeds)) {
 		dev_info(&intf->dev,
 			 "Aiptek tried all speeds, no sane response\n");
+		err = -EINVAL;
 		goto fail2;
 	}