[PATCH nf-next] netfilter: nf_flow_table_offload: fix potential NULL pointer dereference for dst_cache in handling lwtstate

[wenxu@xxxxxxxxx]

From: wenxu <wenxu@xxxxxxxxx>

All the handler in flow_offload_work_handler can be used by both
nft-flowtable and act_ct-flowtable. Flowtable in act_ct zero the
dst_cache ptr in the flow_offload.

Signed-off-by: wenxu <wenxu@xxxxxxxxx>
---
 net/netfilter/nf_flow_table_offload.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/netfilter/nf_flow_table_offload.c b/net/netfilter/nf_flow_table_offload.c
index ca40dfa..9460369 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);
 	}
@@ -483,7 +483,7 @@ static void flow_offload_encap_tunnel(const struct flow_offload *flow,
 	struct dst_entry *dst;
 
 	dst = flow->tuplehash[dir].tuple.dst_cache;
-	if (dst->lwtstate) {
+	if (dst && dst->lwtstate) {
 		struct ip_tunnel_info *tun_info;
 
 		tun_info = lwt_tun_info(dst->lwtstate);
@@ -503,7 +503,7 @@ static void flow_offload_decap_tunnel(const struct flow_offload *flow,
 	struct dst_entry *dst;
 
 	dst = flow->tuplehash[!dir].tuple.dst_cache;
-	if (dst->lwtstate) {
+	if (dst && dst->lwtstate) {
 		struct ip_tunnel_info *tun_info;
 
 		tun_info = lwt_tun_info(dst->lwtstate);
-- 
1.8.3.1