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 04bef83a3358946bfc98a5ecebd1b0003d83d882 Mon Sep 17 00:00:00 2001

From: Nikolay Aleksandrov nikolay@nvidia.com Date: Sun, 11 Jul 2021 12:56:28 +0300 Subject: [PATCH] net: bridge: multicast: fix PIM hello router port marking race

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

Cc: stable@vger.kernel.org Fixes: 91b02d3d133b ("bridge: mcast: add router port on PIM hello message") 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 53c3a9d80d9c..3bbbc6d7b7c3 100644 --- a/net/bridge/br_multicast.c +++ b/net/bridge/br_multicast.c @@ -3264,7 +3264,9 @@ static void br_multicast_pim(struct net_bridge *br, pim_hdr_type(pimhdr) != PIM_TYPE_HELLO) return;

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

static int br_ip4_multicast_mrd_rcv(struct net_bridge *br,