The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 000b7287b67555fee39d39fff75229dedde0dcbf Mon Sep 17 00:00:00 2001

From: Nikolay Aleksandrov nikolay@nvidia.com Date: Sun, 11 Jul 2021 12:56:29 +0300 Subject: [PATCH] net: bridge: multicast: fix MRD advertisement router port marking race

When an MRD advertisement is received on a bridge port with multicast snooping enabled, we mark it as a router port automatically, that includes adding that port to the router port list. The multicast lock protects that list, but it is not acquired in the MRD advertisement case leading to a race condition, we need to take it to fix the race.

Cc: stable@vger.kernel.org Cc: linus.luessing@c0d3.blue Fixes: 4b3087c7e37f ("bridge: Snoop Multicast Router Advertisements") Signed-off-by: Nikolay Aleksandrov nikolay@nvidia.com Signed-off-by: David S. Miller davem@davemloft.net

diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c index 3bbbc6d7b7c3..d0434dc8c03b 100644 --- a/net/bridge/br_multicast.c +++ b/net/bridge/br_multicast.c @@ -3277,7 +3277,9 @@ static int br_ip4_multicast_mrd_rcv(struct net_bridge *br, igmp_hdr(skb)->type != IGMP_MRDISC_ADV) return -ENOMSG;

+ spin_lock(&br->multicast_lock); br_ip4_multicast_mark_router(br, port); + spin_unlock(&br->multicast_lock);

return 0; } @@ -3345,7 +3347,9 @@ static void br_ip6_multicast_mrd_rcv(struct net_bridge *br, if (icmp6_hdr(skb)->icmp6_type != ICMPV6_MRDISC_ADV) return;

+ spin_lock(&br->multicast_lock); br_ip6_multicast_mark_router(br, port); + spin_unlock(&br->multicast_lock); }

static int br_multicast_ipv6_rcv(struct net_bridge *br,