netfilter: nf_tables: disable preemption in nft_update_chain_stats()

This patch fixes the following splat.

[118709.054937] BUG: using smp_processor_id() in preemptible [00000000] code: test/1571
[118709.054970] caller is nft_update_chain_stats.isra.4+0x53/0x97 [nf_tables]
[118709.054980] CPU: 2 PID: 1571 Comm: test Not tainted 4.17.0-rc6+ #335
[...]
[118709.054992] Call Trace:
[118709.055011]  dump_stack+0x5f/0x86
[118709.055026]  check_preemption_disabled+0xd4/0xe4

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/netfilter/nf_tables_core.c b/net/netfilter/nf_tables_core.c
index 942702a2776f6a57313b07c7f88bb67f98710016..40e744572283c709540cccbda7650c4966d845d7 100644 (file)
--- a/net/netfilter/nf_tables_core.c
+++ b/net/netfilter/nf_tables_core.c
@@ -126,15 +126,15 @@ static noinline void nft_update_chain_stats(const struct nft_chain *chain,
        if (!base_chain->stats)
                return;
 
+       local_bh_disable();
        stats = this_cpu_ptr(rcu_dereference(base_chain->stats));
        if (stats) {
-               local_bh_disable();
                u64_stats_update_begin(&stats->syncp);
                stats->pkts++;
                stats->bytes += pkt->skb->len;
                u64_stats_update_end(&stats->syncp);
-               local_bh_enable();
        }
+       local_bh_enable();
 }
 
 struct nft_jumpstack {