From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754817AbdL1Rz5 (ORCPT ); Thu, 28 Dec 2017 12:55:57 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:59095 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754250AbdL1RNw (ORCPT ); Thu, 28 Dec 2017 12:13:52 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "David S. Miller" , "Hannes Frederic Sowa" , "Paolo Abeni" Date: Thu, 28 Dec 2017 17:05:44 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 096/204] udp: fix bcast packet reception In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.52-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Paolo Abeni commit 996b44fcef8f216ea0b6b6e74468c5a77b5e341f upstream. The commit bc044e8db796 ("udp: perform source validation for mcast early demux") does not take into account that broadcast packets lands in the same code path and they need different checks for the source address - notably, zero source address are valid for bcast and invalid for mcast. As a result, 2nd and later broadcast packets with 0 source address landing to the same socket are dropped. This breaks dhcp servers. Since we don't have stringent performance requirements for ingress broadcast traffic, fix it by disabling UDP early demux such traffic. Reported-by: Hannes Frederic Sowa Fixes: bc044e8db796 ("udp: perform source validation for mcast early demux") Signed-off-by: Paolo Abeni Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings --- net/ipv4/udp.c | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -1968,20 +1968,16 @@ int udp_v4_early_demux(struct sk_buff *s iph = ip_hdr(skb); uh = udp_hdr(skb); - if (skb->pkt_type == PACKET_BROADCAST || - skb->pkt_type == PACKET_MULTICAST) { + if (skb->pkt_type == PACKET_MULTICAST) { in_dev = __in_dev_get_rcu(skb->dev); if (!in_dev) return 0; - /* we are supposed to accept bcast packets */ - if (skb->pkt_type == PACKET_MULTICAST) { - ours = ip_check_mc_rcu(in_dev, iph->daddr, iph->saddr, - iph->protocol); - if (!ours) - return 0; - } + ours = ip_check_mc_rcu(in_dev, iph->daddr, iph->saddr, + iph->protocol); + if (!ours) + return 0; sk = __udp4_lib_mcast_demux_lookup(net, uh->dest, iph->daddr, uh->source, iph->saddr, dif);