netfilter: nfnetlink_cttimeout: fix incomplete dumping of objects

Fix broken incomplete object dumping if the list of objects does not
fit into one single netlink message.
Reported-by: Gabriel Lazar <Gabriel.Lazar@com.utcluj.ro>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nfnetlink_cttimeout.c

@@ -220,9 +220,12 @@ ctnl_timeout_dump(struct sk_buff *skb, struct netlink_callback *cb)
 
 	rcu_read_lock();
 	list_for_each_entry_rcu(cur, &cttimeout_list, head) {
-		if (last && cur != last)
-			continue;
+		if (last) {
+			if (cur != last)
+				continue;
 
+			last = NULL;
+		}
 		if (ctnl_timeout_fill_info(skb, NETLINK_CB(cb->skb).portid,
 					   cb->nlh->nlmsg_seq,
 					   NFNL_MSG_TYPE(cb->nlh->nlmsg_type),