linux-kernel - [ 37/48] ip_forward: Drop frames with attached skb->sk

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Message-Id: <20150515080531.857079859@1wt.eu>
Date:	Fri, 15 May 2015 10:06:07 +0200
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Sebastian Poehn <sebastian.poehn@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Ben Hutchings <ben@...adent.org.uk>, Willy Tarreau <w@....eu>
Subject: [ 37/48] ip_forward: Drop frames with attached skb->sk

2.6.32-longterm review patch.  If anyone has any objections, please let me know.

------------------

From: =?latin1?q?Sebastian=20P=F6hn?= <sebastian.poehn@...il.com>

[ Upstream commit 2ab957492d13bb819400ac29ae55911d50a82a13 ]

Initial discussion was:
[FYI] xfrm: Don't lookup sk_policy for timewait sockets

Forwarded frames should not have a socket attached. Especially
tw sockets will lead to panics later-on in the stack.

This was observed with TPROXY assigning a tw socket and broken
policy routing (misconfigured). As a result frame enters
forwarding path instead of input. We cannot solve this in
TPROXY as it cannot know that policy routing is broken.

v2:
Remove useless comment

Signed-off-by: Sebastian Poehn <sebastian.poehn@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
(cherry picked from commit fccb908d23fbae3e941e9294590dd94de6b1d822)

Signed-off-by: Willy Tarreau <w@....eu>
---
 net/ipv4/ip_forward.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/ipv4/ip_forward.c b/net/ipv4/ip_forward.c
index a2991bc..6be434085 100644
--- a/net/ipv4/ip_forward.c
+++ b/net/ipv4/ip_forward.c
@@ -56,6 +56,9 @@ int ip_forward(struct sk_buff *skb)
 	struct rtable *rt;	/* Route we use */
 	struct ip_options * opt	= &(IPCB(skb)->opt);

+	if (unlikely(skb->sk))
+		goto drop;
+
 	if (skb_warn_if_lro(skb))
 		goto drop;

-- 
1.7.12.2.21.g234cd45.dirty

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