[PATCH AUTOSEL 5.0 053/262] netfilter: nf_tables: check the result of dereferencing base_chain->stats

Sasha Levin
2019-03-27T19:30:28Z

From: Li RongQing <lirongqing@baidu.com>

[ Upstream commit a9f5e78c403d2d62ade4f4c85040efc85f4049b8 ]

Check the result of dereferencing base_chain->stats, instead of result
of this_cpu_ptr with NULL.

base_chain->stats maybe be changed to NULL when a chain is updated and a
new NULL counter can be attached.

And we do not need to check returning of this_cpu_ptr since
base_chain->stats is from percpu allocator if it is non-NULL,
this_cpu_ptr returns a valid value.

And fix two sparse error by replacing rcu_access_pointer and
rcu_dereference with READ_ONCE under rcu_read_lock.

Thanks for Eric's help to finish this patch.

Fixes: 009240940e84c1 ("netfilter: nf_tables: don't assume chain stats are set when jumplabel is set")
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Zhang Yu <zhangyu31@baidu.com>
Signed-off-by: Li RongQing <lirongqing@baidu.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/netfilter/nf_tables_core.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/net/netfilter/nf_tables_core.c b/net/netfilter/nf_tables_core.c
index a50500232b0a..7e8dae82ca52 100644
--- a/net/netfilter/nf_tables_core.c
+++ b/net/netfilter/nf_tables_core.c
@@ -98,21 +98,23 @@ 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 __percpu *pstats;
struct nft_stats *stats;

base_chain = nft_base_chain(chain);
- if (!rcu_access_pointer(base_chain->stats))
- return;

- local_bh_disable();
- stats = this_cpu_ptr(rcu_dereference(base_chain->stats));
- if (stats) {
+ rcu_read_lock();
+ pstats = READ_ONCE(base_chain->stats);
+ if (pstats) {
+ local_bh_disable();
+ stats = this_cpu_ptr(pstats);
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();
+ rcu_read_unlock();
}

struct nft_jumpstack {
--
2.19.1