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-Url: https://git.stricted.de/?a=commitdiff_plain;h=fb138c4699c94b16bf9400394142c6d86fe70226;p=GitHub%2Fmt8127%2Fandroid_kernel_alcatel_ttab.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 31ee5c6033df..479e8a63125a 100644
--- a/net/ipv4/ip_forward.c
+++ b/net/ipv4/ip_forward.c
@@ -126,6 +126,9 @@ 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;