netdev - [PATCH 16/20] bridge: netfilter: orphan skb before invoking ip netfilter hooks

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Message-Id: <1383601842-4570-17-git-send-email-pablo@netfilter.org>
Date:	Mon,  4 Nov 2013 22:50:38 +0100
From:	Pablo Neira Ayuso <pablo@...filter.org>
To:	netfilter-devel@...r.kernel.org
Cc:	davem@...emloft.net, netdev@...r.kernel.org
Subject: [PATCH 16/20] bridge: netfilter: orphan skb before invoking ip netfilter hooks

From: Florian Westphal <fw@...len.de>

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@...oulu.fi>
Signed-off-by: Florian Westphal <fw@...len.de>
Acked-by: Eric Dumazet <edumazet@...gle.com>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
 net/bridge/br_netfilter.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c
index f877362..3d55312 100644
--- 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;
 }
 
-- 
1.7.10.4

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