HID: roccat: Use struct_group() to zero kone_mouse_event

In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memset(), avoid intentionally writing across
neighboring fields.

Add struct_group() to mark region of struct kone_mouse_event that should
be initialized to zero.

Cc: Stefan Achatz <erazor_de@users.sourceforge.net>
Cc: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Cc: linux-input@vger.kernel.org
Acked-by: Jiri Kosina <jikos@kernel.org>
Link: https://lore.kernel.org/lkml/nycvar.YFH.7.76.2108201810560.15313@cbobk.fhfr.pmSigned-off-by: Kees Cook <keescook@chromium.org>

drivers/hid/hid-roccat-kone.c

@@ -857,7 +857,7 @@ static int kone_raw_event(struct hid_device *hdev, struct hid_report *report,
 		memcpy(&kone->last_mouse_event, event,
 				sizeof(struct kone_mouse_event));
 	else
-		memset(&event->tilt, 0, 5);
+		memset(&event->wipe, 0, sizeof(event->wipe));
 
 	kone_keep_values_up_to_date(kone, event);
 

drivers/hid/hid-roccat-kone.h

@@ -152,11 +152,13 @@ struct kone_mouse_event {
 	uint16_t x;
 	uint16_t y;
 	uint8_t wheel; /* up = 1, down = -1 */
-	uint8_t tilt; /* right = 1, left = -1 */
-	uint8_t unknown;
-	uint8_t event;
-	uint8_t value; /* press = 0, release = 1 */
-	uint8_t macro_key; /* 0 to 8 */
+	struct_group(wipe,
+		uint8_t tilt; /* right = 1, left = -1 */
+		uint8_t unknown;
+		uint8_t event;
+		uint8_t value; /* press = 0, release = 1 */
+		uint8_t macro_key; /* 0 to 8 */
+	);
 } __attribute__ ((__packed__));
 
 enum kone_mouse_events {