linux-kernel - [PATCH 3.16.y-ckt 034/180] ip_forward: Drop frames with attached skb->sk

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Message-Id: <1430991989-23170-35-git-send-email-luis.henriques@canonical.com>
Date:	Thu,  7 May 2015 10:44:03 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Sebastian Poehn <sebastian.poehn@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 034/180] ip_forward: Drop frames with attached skb->sk

3.16.7-ckt11 -stable review patch.  If anyone has any objections, please let me know.

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

From: =?UTF-8?q?Sebastian=20P=C3=B6hn?= <sebastian.poehn@...il.com>

commit 2ab957492d13bb819400ac29ae55911d50a82a13 upstream.

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: Luis Henriques <luis.henriques@...onical.com>
---
 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 787b3c294ce6..d5410b57da19 100644
--- a/net/ipv4/ip_forward.c
+++ b/net/ipv4/ip_forward.c
@@ -81,6 +81,9 @@ int ip_forward(struct sk_buff *skb)
 	if (skb->pkt_type != PACKET_HOST)
 		goto drop;
 
+	if (unlikely(skb->sk))
+		goto drop;
+
 	if (skb_warn_if_lro(skb))
 		goto drop;
 
--
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