From: Sebastian Pöhn <sebastian.poehn@gmail.com>
Date: Mon, 20 Apr 2015 07:19:20 +0000 (+0200)
Subject: ip_forward: Drop frames with attached skb->sk
X-Git-Tag: v3.19.7~174
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cf5bab3a832bea1f13b52a36eb7b8667260e64e7;p=thirdparty%2Fkernel%2Fstable.git

ip_forward: Drop frames with attached skb->sk

[ 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@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/net/ipv4/ip_forward.c b/net/ipv4/ip_forward.c
index 787b3c294ce67..d5410b57da197 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;