linux-kernel - [PATCH 4.19 420/421] net: bridge: multicast: fix PIM hello router port marking race

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Date:   Mon, 19 Jul 2021 16:53:51 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Nikolay Aleksandrov <nikolay@...dia.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.19 420/421] net: bridge: multicast: fix PIM hello router port marking race

From: Nikolay Aleksandrov <nikolay@...dia.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@...r.kernel.org
Fixes: 91b02d3d133b ("bridge: mcast: add router port on PIM hello message")
Signed-off-by: Nikolay Aleksandrov <nikolay@...dia.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/bridge/br_multicast.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -1791,7 +1791,9 @@ static void br_multicast_pim(struct net_
 	    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,