From: Linus Lüssing linus.luessing@c0d3.blue
[ Upstream commit 99014088156cd78867d19514a0bc771c4b86b93b ]
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 linus.luessing@c0d3.blue Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- 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 257ac4e25f6d..5f89ae3ae4d8 100644 --- a/net/bridge/br_multicast.c +++ b/net/bridge/br_multicast.c @@ -3075,25 +3075,14 @@ 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, @@ -3107,18 +3096,12 @@ 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