media: rc: ensure we do not read out of bounds

If rc_validate_filter() is called for CEC or XMP, then we would read
beyond the end of the array.
Suggested-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NSean Young <sean@mess.org>
Signed-off-by: NMauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/rc/rc-main.c

@@ -733,7 +733,7 @@ EXPORT_SYMBOL_GPL(rc_keydown_notimeout);
 static int rc_validate_filter(struct rc_dev *dev,
 			      struct rc_scancode_filter *filter)
 {
-	static u32 masks[] = {
+	static const u32 masks[] = {
 		[RC_TYPE_RC5] = 0x1f7f,
 		[RC_TYPE_RC5X_20] = 0x1f7f3f,
 		[RC_TYPE_RC5_SZ] = 0x2fff,
@@ -757,6 +757,9 @@ static int rc_validate_filter(struct rc_dev *dev,
 	u32 s = filter->data;
 	enum rc_type protocol = dev->wakeup_protocol;
 
+	if (protocol >= ARRAY_SIZE(masks))
+		return -EINVAL;
+
 	switch (protocol) {
 	case RC_TYPE_NECX:
 		if ((((s >> 16) ^ ~(s >> 8)) & 0xff) == 0)