netfilter: nf_tables: do not leave chain stats enabled on error

Error might occur later in the nf_tables_addchain() codepath, enable
static key only after transaction has been created.

Fixes: 9f08ea84 ("netfilter: nf_tables: keep chain counters away from hot path")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_api.c

@@ -2195,9 +2195,9 @@ static int nf_tables_addchain(struct nft_ctx *ctx, u8 family, u8 genmask,
 			      struct netlink_ext_ack *extack)
 {
 	const struct nlattr * const *nla = ctx->nla;
+	struct nft_stats __percpu *stats = NULL;
 	struct nft_table *table = ctx->table;
 	struct nft_base_chain *basechain;
-	struct nft_stats __percpu *stats;
 	struct net *net = ctx->net;
 	char name[NFT_NAME_MAXLEN];
 	struct nft_rule_blob *blob;
@@ -2235,7 +2235,6 @@ static int nf_tables_addchain(struct nft_ctx *ctx, u8 family, u8 genmask,
 				return PTR_ERR(stats);
 			}
 			rcu_assign_pointer(basechain->stats, stats);
-			static_branch_inc(&nft_counters_enabled);
 		}
 
 		err = nft_basechain_init(basechain, family, &hook, flags);
@@ -2318,6 +2317,9 @@ static int nf_tables_addchain(struct nft_ctx *ctx, u8 family, u8 genmask,
 		goto err_unregister_hook;
 	}
 
+	if (stats)
+		static_branch_inc(&nft_counters_enabled);
+
 	table->use++;
 
 	return 0;