netfilter: nf_tables: add nft_dereference() macro

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/netfilter/nf_tables.h

@@ -3,6 +3,7 @@
 
 #include <linux/list.h>
 #include <linux/netfilter.h>
+#include <linux/netfilter/nfnetlink.h>
 #include <linux/netfilter/x_tables.h>
 #include <linux/netfilter/nf_tables.h>
 #include <net/netlink.h>
@@ -521,6 +522,9 @@ void nft_unregister_chain_type(const struct nf_chain_type *);
 int nft_register_expr(struct nft_expr_type *);
 void nft_unregister_expr(struct nft_expr_type *);
 
+#define nft_dereference(p)					\
+	nfnl_dereference(p, NFNL_SUBSYS_NFTABLES)
+
 #define MODULE_ALIAS_NFT_FAMILY(family)	\
 	MODULE_ALIAS("nft-afinfo-" __stringify(family))
 

net/netfilter/nf_tables_api.c

@@ -794,9 +794,8 @@ nf_tables_counters(struct nft_base_chain *chain, const struct nlattr *attr)
 	stats->pkts = be64_to_cpu(nla_get_be64(tb[NFTA_COUNTER_PACKETS]));
 
 	if (chain->stats) {
-		/* nfnl_lock is held, add some nfnl function for this, later */
 		struct nft_stats __percpu *oldstats =
-			rcu_dereference_protected(chain->stats, 1);
+				nft_dereference(chain->stats);
 
 		rcu_assign_pointer(chain->stats, newstats);
 		synchronize_rcu();