From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:47746 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934137AbdJJUHC (ORCPT ); Tue, 10 Oct 2017 16:07:02 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Hannes Frederic Sowa , Paolo Abeni , "David S. Miller" Subject: [PATCH 4.13 159/160] udp: fix bcast packet reception Date: Tue, 10 Oct 2017 21:51:27 +0200 Message-Id: <20171010190555.953573520@linuxfoundation.org> In-Reply-To: <20171010190548.690912997@linuxfoundation.org> References: <20171010190548.690912997@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.13-stable 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: Greg Kroah-Hartman --- net/ipv4/udp.c | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -2235,20 +2235,16 @@ 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);