From patchwork Sun Apr 25 15:27:35 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Linus_L=C3=BCssing?= X-Patchwork-Id: 12223359 X-Patchwork-Delegate: kuba@kernel.org Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1BCC4C433B4 for ; Sun, 25 Apr 2021 15:36:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EB60161078 for ; Sun, 25 Apr 2021 15:36:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230388AbhDYPh0 (ORCPT ); Sun, 25 Apr 2021 11:37:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56268 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230194AbhDYPhZ (ORCPT ); Sun, 25 Apr 2021 11:37:25 -0400 X-Greylist: delayed 492 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Sun, 25 Apr 2021 08:36:45 PDT Received: from mail.aperture-lab.de (mail.aperture-lab.de [IPv6:2a01:4f8:c2c:665b::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B4D21C061574; Sun, 25 Apr 2021 08:36:45 -0700 (PDT) Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 1DAAD3EB2E; Sun, 25 Apr 2021 17:28:28 +0200 (CEST) From: =?utf-8?q?Linus_L=C3=BCssing?= To: netdev@vger.kernel.org Cc: Roopa Prabhu , Nikolay Aleksandrov , Jakub Kicinski , "David S . Miller" , bridge@lists.linux-foundation.org, linux-kernel@vger.kernel.org, =?utf-8?q?Linus_L=C3=BCssing?= Subject: [PATCH net] net: bridge: mcast: fix broken length + header check for MRDv6 Adv. Date: Sun, 25 Apr 2021 17:27:35 +0200 Message-Id: <20210425152736.8421-1-linus.luessing@c0d3.blue> MIME-Version: 1.0 X-Last-TLS-Session-Version: TLSv1.2 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org The IPv6 Multicast Router Advertisements parsing has the following two issues: For one thing, ICMPv6 MRD Advertisements are smaller than ICMPv6 MLD messages (ICMPv6 MRD Adv.: 8 bytes vs. ICMPv6 MLDv1/2: >= 24 bytes, assuming MLDv2 Reports with at least one multicast address entry). When ipv6_mc_check_mld_msg() tries to parse an Multicast Router Advertisement its MLD length check will fail - and it will wrongly return -EINVAL, even if we have a valid MRD Advertisement. With the returned -EINVAL the bridge code will assume a broken packet and will wrongly discard it, potentially leading to multicast packet loss towards multicast routers. The second issue is the MRD header parsing in br_ip6_multicast_mrd_rcv(): It wrongly checks for an ICMPv6 header immediately after the IPv6 header (IPv6 next header type). However according to RFC4286, section 2 all MRD messages contain a Router Alert option (just like MLD). So instead there is an IPv6 Hop-by-Hop option for the Router Alert between the IPv6 and ICMPv6 header, again leading to the bridge wrongly discarding Multicast Router Advertisements. To fix these two issues, introduce a new return value -ENODATA to ipv6_mc_check_mld() to indicate a valid ICMPv6 packet with a hop-by-hop option which is not an MLD but potentially an MRD packet. This also simplifies further parsing in the bridge code, as ipv6_mc_check_mld() already fully checks the ICMPv6 header and hop-by-hop option. These issues were found and fixed with the help of the mrdisc tool (https://github.com/troglobit/mrdisc). Fixes: 4b3087c7e37f ("bridge: Snoop Multicast Router Advertisements") Signed-off-by: Linus Lüssing --- include/net/addrconf.h | 1 - net/bridge/br_multicast.c | 33 ++++++++------------------------- net/ipv6/mcast_snoop.c | 12 +++++++----- 3 files changed, 15 insertions(+), 31 deletions(-) diff --git a/include/net/addrconf.h b/include/net/addrconf.h index 18f783dcd55f..78ea3e332688 100644 --- a/include/net/addrconf.h +++ b/include/net/addrconf.h @@ -233,7 +233,6 @@ void ipv6_mc_unmap(struct inet6_dev *idev); void ipv6_mc_remap(struct inet6_dev *idev); void ipv6_mc_init_dev(struct inet6_dev *idev); void ipv6_mc_destroy_dev(struct inet6_dev *idev); -int ipv6_mc_check_icmpv6(struct sk_buff *skb); int ipv6_mc_check_mld(struct sk_buff *skb); void addrconf_dad_failure(struct sk_buff *skb, struct inet6_ifaddr *ifp); diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c index 9d265447d654..229309d7b4ff 100644 --- a/net/bridge/br_multicast.c +++ b/net/bridge/br_multicast.c @@ -3152,25 +3152,14 @@ static int br_multicast_ipv4_rcv(struct net_bridge *br, } #if IS_ENABLED(CONFIG_IPV6) -static int br_ip6_multicast_mrd_rcv(struct net_bridge *br, - struct net_bridge_port *port, - struct sk_buff *skb) +static void br_ip6_multicast_mrd_rcv(struct net_bridge *br, + struct net_bridge_port *port, + struct sk_buff *skb) { - int ret; - - if (ipv6_hdr(skb)->nexthdr != IPPROTO_ICMPV6) - return -ENOMSG; - - ret = ipv6_mc_check_icmpv6(skb); - if (ret < 0) - return ret; - if (icmp6_hdr(skb)->icmp6_type != ICMPV6_MRDISC_ADV) - return -ENOMSG; + return; br_multicast_mark_router(br, port); - - return 0; } static int br_multicast_ipv6_rcv(struct net_bridge *br, @@ -3184,18 +3173,12 @@ static int br_multicast_ipv6_rcv(struct net_bridge *br, err = ipv6_mc_check_mld(skb); - if (err == -ENOMSG) { + if (err == -ENOMSG || err == -ENODATA) { if (!ipv6_addr_is_ll_all_nodes(&ipv6_hdr(skb)->daddr)) BR_INPUT_SKB_CB(skb)->mrouters_only = 1; - - if (ipv6_addr_is_all_snoopers(&ipv6_hdr(skb)->daddr)) { - err = br_ip6_multicast_mrd_rcv(br, port, skb); - - if (err < 0 && err != -ENOMSG) { - br_multicast_err_count(br, port, skb->protocol); - return err; - } - } + if (err == -ENODATA && + ipv6_addr_is_all_snoopers(&ipv6_hdr(skb)->daddr)) + br_ip6_multicast_mrd_rcv(br, port, skb); return 0; } else if (err < 0) { diff --git a/net/ipv6/mcast_snoop.c b/net/ipv6/mcast_snoop.c index d3d6b6a66e5f..04d5fcdfa6e0 100644 --- a/net/ipv6/mcast_snoop.c +++ b/net/ipv6/mcast_snoop.c @@ -109,7 +109,7 @@ static int ipv6_mc_check_mld_msg(struct sk_buff *skb) struct mld_msg *mld; if (!ipv6_mc_may_pull(skb, len)) - return -EINVAL; + return -ENODATA; mld = (struct mld_msg *)skb_transport_header(skb); @@ -122,7 +122,7 @@ static int ipv6_mc_check_mld_msg(struct sk_buff *skb) case ICMPV6_MGM_QUERY: return ipv6_mc_check_mld_query(skb); default: - return -ENOMSG; + return -ENODATA; } } @@ -131,7 +131,7 @@ static inline __sum16 ipv6_mc_validate_checksum(struct sk_buff *skb) return skb_checksum_validate(skb, IPPROTO_ICMPV6, ip6_compute_pseudo); } -int ipv6_mc_check_icmpv6(struct sk_buff *skb) +static int ipv6_mc_check_icmpv6(struct sk_buff *skb) { unsigned int len = skb_transport_offset(skb) + sizeof(struct icmp6hdr); unsigned int transport_len = ipv6_transport_len(skb); @@ -150,7 +150,6 @@ int ipv6_mc_check_icmpv6(struct sk_buff *skb) return 0; } -EXPORT_SYMBOL(ipv6_mc_check_icmpv6); /** * ipv6_mc_check_mld - checks whether this is a sane MLD packet @@ -161,7 +160,10 @@ EXPORT_SYMBOL(ipv6_mc_check_icmpv6); * * -EINVAL: A broken packet was detected, i.e. it violates some internet * standard - * -ENOMSG: IP header validation succeeded but it is not an MLD packet. + * -ENOMSG: IP header validation succeeded but it is not an ICMPv6 packet + * with a hop-by-hop option. + * -ENODATA: IP+ICMPv6 header with hop-by-hop option validation succeeded + * but it is not an MLD packet. * -ENOMEM: A memory allocation failure happened. * * Caller needs to set the skb network header and free any returned skb if it