netfilter: ipset: Fix static checker warning in ip_set_core.c

Dan Carpenter reported the following static checker warning:

        net/netfilter/ipset/ip_set_core.c:1414 call_ad()
        error: 'nlh->nlmsg_len' from user is not capped properly

The payload size is limited now by the max size of size_t.
Signed-off-by: NJozsef Kadlecsik <kadlec@blackhole.kfki.hu>

net/netfilter/ipset/ip_set_core.c

@@ -1397,7 +1397,8 @@ call_ad(struct sock *ctnl, struct sk_buff *skb, struct ip_set *set,
 		struct nlmsghdr *rep, *nlh = nlmsg_hdr(skb);
 		struct sk_buff *skb2;
 		struct nlmsgerr *errmsg;
-		size_t payload = sizeof(*errmsg) + nlmsg_len(nlh);
+		size_t payload = min(SIZE_MAX,
+				     sizeof(*errmsg) + nlmsg_len(nlh));
 		int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
 		struct nlattr *cda[IPSET_ATTR_CMD_MAX+1];
 		struct nlattr *cmdattr;