netdev - [PATCH net-next] netfilter: flowtable: Fix accessing null dst entry

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Message-Id: <1585133608-25295-1-git-send-email-paulb@mellanox.com>
Date:   Wed, 25 Mar 2020 12:53:28 +0200
From:   Paul Blakey <paulb@...lanox.com>
To:     Paul Blakey <paulb@...lanox.com>, Oz Shlomo <ozsh@...lanox.com>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Majd Dibbiny <majd@...lanox.com>,
        Roi Dayan <roid@...lanox.com>, netdev@...r.kernel.org,
        Saeed Mahameed <saeedm@...lanox.com>
Cc:     netfilter-devel@...r.kernel.org
Subject: [PATCH net-next] netfilter: flowtable: Fix accessing null dst entry

Unlink nft flow table flows, flows from act_ct tables don't have route,
and so don't have a dst_entry. nf_flow_rule_match() tries to deref
this null dst_entry regardless.

Fix that by checking for dst entry exists, and if not, skip
tunnel match.

Fixes: cfab6dbd0ecf ("netfilter: flowtable: add tunnel match offload support")
Signed-off-by: Paul Blakey <paulb@...lanox.com>
---
 net/netfilter/nf_flow_table_offload.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/netfilter/nf_flow_table_offload.c b/net/netfilter/nf_flow_table_offload.c
index ca40dfa..6518a91 100644
--- a/net/netfilter/nf_flow_table_offload.c
+++ b/net/netfilter/nf_flow_table_offload.c
@@ -92,7 +92,7 @@ static int nf_flow_rule_match(struct nf_flow_match *match,
 	NF_FLOW_DISSECTOR(match, FLOW_DISSECTOR_KEY_TCP, tcp);
 	NF_FLOW_DISSECTOR(match, FLOW_DISSECTOR_KEY_PORTS, tp);
 
-	if (other_dst->lwtstate) {
+	if (other_dst && other_dst->lwtstate) {
 		tun_info = lwt_tun_info(other_dst->lwtstate);
 		nf_flow_rule_lwt_match(match, tun_info);
 	}
-- 
1.8.3.1