mpls: Use nlmsg_payload in mpls_valid_getroute_req

Leverage the new nlmsg_payload() helper to avoid checking for message
size and then reading the nlmsg data.

Signed-off-by: Breno Leitao <[email protected]>
Reviewed-by: Kuniyuki Iwashima <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: leitao

net/mpls/af_mpls.c

@@ -2288,7 +2288,8 @@ static int mpls_valid_getroute_req(struct sk_buff *skb,
 	struct rtmsg *rtm;
 	int i, err;
 
-	if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(*rtm))) {
+	rtm = nlmsg_payload(nlh, sizeof(*rtm));
+	if (!rtm) {
 		NL_SET_ERR_MSG_MOD(extack,
 				   "Invalid header for get route request");
 		return -EINVAL;
@@ -2298,7 +2299,6 @@ static int mpls_valid_getroute_req(struct sk_buff *skb,
 		return nlmsg_parse_deprecated(nlh, sizeof(*rtm), tb, RTA_MAX,
 					      rtm_mpls_policy, extack);
 
-	rtm = nlmsg_data(nlh);
 	if ((rtm->rtm_dst_len && rtm->rtm_dst_len != 20) ||
 	    rtm->rtm_src_len || rtm->rtm_tos || rtm->rtm_table ||
 	    rtm->rtm_protocol || rtm->rtm_scope || rtm->rtm_type) {