bridge: netfilter: orphan skb before invoking ip netfilter hooks

Pekka Pietikäinen reports xt_socket behavioural change after commit
00028aa37098o (netfilter: xt_socket: use IP early demux).

Reason is xt_socket now no longer does an unconditional sk lookup -
it re-uses existing skb->sk if possible, assuming ->sk was set by
ip early demux.

However, when netfilter is invoked via bridge, this can cause 'bogus'
sockets to be examined by the match, e.g. a 'tun' device socket.

bridge netfilter should orphan the skb just like the routing path
before invoking ipv4/ipv6 netfilter hooks to avoid this.

Reported-and-tested-by: Pekka Pietikäinen <pp@ee.oulu.fi>
Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c
index f877362..3d55312 100644 (file)
--- a/net/bridge/br_netfilter.c
+++ b/net/bridge/br_netfilter.c
@@ -559,6 +559,8 @@ static struct net_device *setup_pre_routing(struct sk_buff *skb)
        else if (skb->protocol == htons(ETH_P_PPP_SES))
                nf_bridge->mask |= BRNF_PPPoE;
 
+       /* Must drop socket now because of tproxy. */
+       skb_orphan(skb);
        return skb->dev;
 }