releases/3.4.43/tcp-incoming-connections-might-use-wrong-route-under-synflood.patch

From f69107361c6ad91517a8b0323fb96c928804864c Mon Sep 17 00:00:00 2001
From: Dmitry Popov <dp@highloadlab.com>
Date: Thu, 11 Apr 2013 08:55:07 +0000
Subject: tcp: incoming connections might use wrong route under synflood


From: Dmitry Popov <dp@highloadlab.com>

[ Upstream commit d66954a066158781ccf9c13c91d0316970fe57b6 ]

There is a bug in cookie_v4_check (net/ipv4/syncookies.c):
	flowi4_init_output(&fl4, 0, sk->sk_mark, RT_CONN_FLAGS(sk),
			   RT_SCOPE_UNIVERSE, IPPROTO_TCP,
			   inet_sk_flowi_flags(sk),
			   (opt && opt->srr) ? opt->faddr : ireq->rmt_addr,
			   ireq->loc_addr, th->source, th->dest);

Here we do not respect sk->sk_bound_dev_if, therefore wrong dst_entry may be
taken. This dst_entry is used by new socket (get_cookie_sock ->
tcp_v4_syn_recv_sock), so its packets may take the wrong path.

Signed-off-by: Dmitry Popov <dp@highloadlab.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv4/syncookies.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -347,8 +347,8 @@ struct sock *cookie_v4_check(struct sock
 	 * hasn't changed since we received the original syn, but I see
 	 * no easy way to do this.
 	 */
-	flowi4_init_output(&fl4, 0, sk->sk_mark, RT_CONN_FLAGS(sk),
-			   RT_SCOPE_UNIVERSE, IPPROTO_TCP,
+	flowi4_init_output(&fl4, sk->sk_bound_dev_if, sk->sk_mark,
+			   RT_CONN_FLAGS(sk), RT_SCOPE_UNIVERSE, IPPROTO_TCP,
 			   inet_sk_flowi_flags(sk),
 			   (opt && opt->srr) ? opt->faddr : ireq->rmt_addr,
 			   ireq->loc_addr, th->source, th->dest);