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

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

[Nikolay Aleksandrov]

From: Nikolay Aleksandrov <nikolay@nvidia.com>

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@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>
---
 net/bridge/br_multicast.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index b24782d53474..4e3ff0b55ec1 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -1763,7 +1763,9 @@ static void br_multicast_pim(struct net_bridge *br,
 	    pim_hdr_type(pimhdr) != PIM_TYPE_HELLO)
 		return;
 
+	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,
-- 
2.31.1