netdev - [PATCH net 1/2] net: bridge: multicast: fix PIM hello router port marking race

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Message-Id: <20210711095629.2986949-2-razor@blackwall.org>
Date:   Sun, 11 Jul 2021 12:56:28 +0300
From:   Nikolay Aleksandrov <razor@...ckwall.org>
To:     netdev@...r.kernel.org
Cc:     stable@...r.kernel.org, roopa@...dia.com,
        bridge@...ts.linux-foundation.org,
        Nikolay Aleksandrov <nikolay@...dia.com>
Subject: [PATCH net 1/2] net: bridge: multicast: fix PIM hello router port marking race

From: Nikolay Aleksandrov <nikolay@...dia.com>

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>
---
 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 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,
-- 
2.31.1