linux-kernel - [PATCH 4.19 33/50] net: bridge: mcast: fix stale ipv6 hdr pointer when handling v6 query

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Message-Id: <20190726152304.047028867@linuxfoundation.org>
Date:   Fri, 26 Jul 2019 17:25:08 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Nikolay Aleksandrov <nikolay@...ulusnetworks.com>,
        Martin Weinelt <martin@...uxlounge.net>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.19 33/50] net: bridge: mcast: fix stale ipv6 hdr pointer when handling v6 query

From: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>

[ Upstream commit 3b26a5d03d35d8f732d75951218983c0f7f68dff ]

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>
Tested-by: Martin Weinelt <martin@...uxlounge.net>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/bridge/br_multicast.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -1510,7 +1510,6 @@ static int br_ip6_multicast_query(struct
 				  struct sk_buff *skb,
 				  u16 vid)
 {
-	const struct ipv6hdr *ip6h = ipv6_hdr(skb);
 	struct mld_msg *mld;
 	struct net_bridge_mdb_entry *mp;
 	struct mld2_query *mld2q;
@@ -1554,7 +1553,7 @@ static int br_ip6_multicast_query(struct
 
 	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);