netfilter: nf_tables: don't assume chain stats are set when jumplabel is set

nft_chain_stats_replace() and all other spots assume ->stats can be
NULL, but nft_update_chain_stats does not.  It must do this check,
just because the jump label is set doesn't mean all basechains have stats
assigned.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_core.c

@@ -119,15 +119,22 @@ DEFINE_STATIC_KEY_FALSE(nft_counters_enabled);
 static noinline void nft_update_chain_stats(const struct nft_chain *chain,
 					    const struct nft_pktinfo *pkt)
 {
+	struct nft_base_chain *base_chain;
 	struct nft_stats *stats;
 
+	base_chain = nft_base_chain(chain);
+	if (!base_chain->stats)
+		return;
+
+	stats = this_cpu_ptr(rcu_dereference(base_chain->stats));
+	if (stats) {
 		local_bh_disable();
-	stats = this_cpu_ptr(rcu_dereference(nft_base_chain(chain)->stats));
 		u64_stats_update_begin(&stats->syncp);
 		stats->pkts++;
 		stats->bytes += pkt->skb->len;
 		u64_stats_update_end(&stats->syncp);
 		local_bh_enable();
+	}
 }
 
 struct nft_jumpstack {