[PATCH nf v3 2/3] netfilter: nf_flow_table_offload: check the status of dst_neigh

[wenxu@ucloud.cn]

From: wenxu <wenxu@ucloud.cn>

It is better to get the dst_neigh with neigh->lock and check the
nud_state is VALID. If there is not neigh previous, the lookup will
Create a non NUD_VALID with 00:00:00:00:00:00 mac.

Fixes: c29f74e0df7a ("netfilter: nf_flow_table: hardware offload support")
Signed-off-by: wenxu <wenxu@ucloud.cn>
---
 net/netfilter/nf_flow_table_offload.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/nf_flow_table_offload.c b/net/netfilter/nf_flow_table_offload.c
index ee9edbe..92b0bd2 100644
--- a/net/netfilter/nf_flow_table_offload.c
+++ b/net/netfilter/nf_flow_table_offload.c
@@ -170,8 +170,10 @@ static int flow_offload_eth_dst(struct net *net,
 	struct flow_action_entry *entry1 = flow_action_entry_next(flow_rule);
 	const void *daddr = &flow->tuplehash[!dir].tuple.src_v4;
 	const struct dst_entry *dst_cache;
+	unsigned char ha[ETH_ALEN];
 	struct neighbour *n;
 	u32 mask, val;
+	u8 nud_state;
 	u16 val16;
 
 	dst_cache = flow->tuplehash[dir].tuple.dst_cache;
@@ -179,13 +181,23 @@ static int flow_offload_eth_dst(struct net *net,
 	if (!n)
 		return -ENOENT;
 
+	read_lock_bh(&n->lock);
+	nud_state = n->nud_state;
+	ether_addr_copy(ha, n->ha);
+	read_unlock_bh(&n->lock);
+
+	if (!(nud_state & NUD_VALID)) {
+		neigh_release(n);
+		return -ENOENT;
+	}
+
 	mask = ~0xffffffff;
-	memcpy(&val, n->ha, 4);
+	memcpy(&val, ha, 4);
 	flow_offload_mangle(entry0, FLOW_ACT_MANGLE_HDR_TYPE_ETH, 0,
 			    &val, &mask);
 
 	mask = ~0x0000ffff;
-	memcpy(&val16, n->ha + 4, 2);
+	memcpy(&val16, ha + 4, 2);
 	val = val16;
 	flow_offload_mangle(entry1, FLOW_ACT_MANGLE_HDR_TYPE_ETH, 4,
 			    &val, &mask);
-- 
1.8.3.1