HID: logitech-hidpp: check WTP report length

Malicious USB devices can send bogus reports smaller than the expected
buffer size. Ensure that the length for WTP reports is valid to avoid
reading out of bounds.
Signed-off-by: Peter Wu <peter@lekensteyn.nl>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-logitech-hidpp.c

@@ -794,6 +794,11 @@ static int wtp_raw_event(struct hid_device *hdev, u8 *data, int size)
 
 	switch (data[0]) {
 	case 0x02:
+		if (size < 2) {
+			hid_err(hdev, "Received HID report of bad size (%d)",
+				size);
+			return 1;
+		}
 		if (hidpp->quirks & HIDPP_QUIRK_WTP_PHYSICAL_BUTTONS) {
 			input_event(wd->input, EV_KEY, BTN_LEFT,
 					!!(data[1] & 0x01));
@@ -806,6 +811,7 @@ static int wtp_raw_event(struct hid_device *hdev, u8 *data, int size)
 			return wtp_mouse_raw_xy_event(hidpp, &data[7]);
 		}
 	case REPORT_ID_HIDPP_LONG:
+		/* size is already checked in hidpp_raw_event. */
 		if ((report->fap.feature_index != wd->mt_feature_index) ||
 		    (report->fap.funcindex_clientid != EVENT_TOUCHPAD_RAW_XY))
 			return 1;