netfilter: nf_tables: don't update chain with unset counters

Fix possible replacement of the per-cpu chain counters by null
pointer when updating an existing chain in the commit path.

Reported-by: Matteo Croce <technoboy85@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index c6f9d3d18ed1..9aa31f11056d 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -899,6 +899,9 @@ static struct nft_stats __percpu *nft_stats_alloc(const struct nlattr *attr)
 static void nft_chain_stats_replace(struct nft_base_chain *chain,
                                     struct nft_stats __percpu *newstats)
 {
+        if (newstats == NULL)
+                return;
+
         if (chain->stats) {
                 struct nft_stats __percpu *oldstats =
                                 nft_dereference(chain->stats);