netdev - [PATCH net 2/4] net: bridge: mcast: fix stale ipv6 hdr pointer when handling v6 query

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Message-Id: <20190702120021.13096-3-nikolay@cumulusnetworks.com>
Date:   Tue,  2 Jul 2019 15:00:19 +0300
From:   Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
To:     netdev@...r.kernel.org
Cc:     roopa@...ulusnetworks.com, davem@...emloft.net,
        martin@...uxlounge.net, bridge@...ts.linux-foundation.org,
        yoshfuji@...ux-ipv6.org,
        Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
Subject: [PATCH net 2/4] net: bridge: mcast: fix stale ipv6 hdr pointer when handling v6 query

We get a pointer to the ipv6 hdr in br_ip6_multicast_query but we may
call pskb_may_pull afterwards and end up using a stale pointer.
So use the header directly, it's just 1 place where it's needed.

Fixes: 08b202b67264 ("bridge br_multicast: IPv6 MLD support.")
Signed-off-by: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
---
 net/bridge/br_multicast.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index f37897e7b97b..3d8deac2353d 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -1279,7 +1279,6 @@ static int br_ip6_multicast_query(struct net_bridge *br,
 				  u16 vid)
 {
 	unsigned int transport_len = ipv6_transport_len(skb);
-	const struct ipv6hdr *ip6h = ipv6_hdr(skb);
 	struct mld_msg *mld;
 	struct net_bridge_mdb_entry *mp;
 	struct mld2_query *mld2q;
@@ -1323,7 +1322,7 @@ static int br_ip6_multicast_query(struct net_bridge *br,
 
 	if (is_general_query) {
 		saddr.proto = htons(ETH_P_IPV6);
-		saddr.u.ip6 = ip6h->saddr;
+		saddr.u.ip6 = ipv6_hdr(skb)->saddr;
 
 		br_multicast_query_received(br, port, &br->ip6_other_query,
 					    &saddr, max_delay);
-- 
2.21.0