Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754246AbcKSJZx (ORCPT ); Sat, 19 Nov 2016 04:25:53 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:58528 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753743AbcKSJZu (ORCPT ); Sat, 19 Nov 2016 04:25:50 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Stephen Suryaputra Lin , "David S. Miller" Subject: [PATCH 4.8 21/49] ipv4: use new_gw for redirect neigh lookup Date: Sat, 19 Nov 2016 10:23:13 +0100 Message-Id: <20161119092039.984351859@linuxfoundation.org> X-Mailer: git-send-email 2.10.2 In-Reply-To: <20161119092036.698705716@linuxfoundation.org> References: <20161119092036.698705716@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1913 Lines: 51 4.8-stable review patch. If anyone has any objections, please let me know. ------------------ From: Stephen Suryaputra Lin [ Upstream commit 969447f226b451c453ddc83cac6144eaeac6f2e3 ] In v2.6, ip_rt_redirect() calls arp_bind_neighbour() which returns 0 and then the state of the neigh for the new_gw is checked. If the state isn't valid then the redirected route is deleted. This behavior is maintained up to v3.5.7 by check_peer_redirect() because rt->rt_gateway is assigned to peer->redirect_learned.a4 before calling ipv4_neigh_lookup(). After commit 5943634fc559 ("ipv4: Maintain redirect and PMTU info in struct rtable again."), ipv4_neigh_lookup() is performed without the rt_gateway assigned to the new_gw. In the case when rt_gateway (old_gw) isn't zero, the function uses it as the key. The neigh is most likely valid since the old_gw is the one that sends the ICMP redirect message. Then the new_gw is assigned to fib_nh_exception. The problem is: the new_gw ARP may never gets resolved and the traffic is blackholed. So, use the new_gw for neigh lookup. Changes from v1: - use __ipv4_neigh_lookup instead (per Eric Dumazet). Fixes: 5943634fc559 ("ipv4: Maintain redirect and PMTU info in struct rtable again.") Signed-off-by: Stephen Suryaputra Lin Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv4/route.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -753,7 +753,9 @@ static void __ip_do_redirect(struct rtab goto reject_redirect; } - n = ipv4_neigh_lookup(&rt->dst, NULL, &new_gw); + n = __ipv4_neigh_lookup(rt->dst.dev, new_gw); + if (!n) + n = neigh_create(&arp_tbl, &new_gw, rt->dst.dev); if (!IS_ERR(n)) { if (!(n->nud_state & NUD_VALID)) { neigh_event_send(n, NULL);