[PATCH 4.14 315/315] net: bridge: multicast: fix PIM hello router port marking race

From: Greg Kroah-Hartman
Date: Mon Jul 19 2021 - 11:53:24 EST

From: Nikolay Aleksandrov <nikolay@xxxxxxxxxx>

commit 04bef83a3358946bfc98a5ecebd1b0003d83d882 upstream.

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@xxxxxxxxxxxxxxx
Fixes: 91b02d3d133b ("bridge: mcast: add router port on PIM hello message")
Signed-off-by: Nikolay Aleksandrov <nikolay@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
net/bridge/br_multicast.c | 2 ++
1 file changed, 2 insertions(+)

--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -1763,7 +1763,9 @@ static void br_multicast_pim(struct net_
pim_hdr_type(pimhdr) != PIM_TYPE_HELLO)

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

static int br_multicast_ipv4_rcv(struct net_bridge *br,