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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Nikolay Aleksandrov <nikolay@cumulusnetworks.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.4 139/168] net: bridge: multicast: use rcu to access port list from br_multicast_start_querier
Date:   Wed, 24 Apr 2019 19:09:43 +0200
Message-Id: <20190424170931.485603527@linuxfoundation.org>
In-Reply-To: <20190424170923.452349382@linuxfoundation.org>
References: <20190424170923.452349382@linuxfoundation.org>
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From: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>

[ Upstream commit c5b493ce192bd7a4e7bd073b5685aad121eeef82 ]

br_multicast_start_querier() walks over the port list but it can be
called from a timer with only multicast_lock held which doesn't protect
the port list, so use RCU to walk over it.

Fixes: c83b8fab06fc ("bridge: Restart queries when last querier expires")
Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/bridge/br_multicast.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -1894,7 +1894,8 @@ static void br_multicast_start_querier(s
 
 	__br_multicast_open(br, query);
 
-	list_for_each_entry(port, &br->port_list, list) {
+	rcu_read_lock();
+	list_for_each_entry_rcu(port, &br->port_list, list) {
 		if (port->state == BR_STATE_DISABLED ||
 		    port->state == BR_STATE_BLOCKING)
 			continue;
@@ -1906,6 +1907,7 @@ static void br_multicast_start_querier(s
 			br_multicast_enable(&port->ip6_own_query);
 #endif
 	}
+	rcu_read_unlock();
 }
 
 int br_multicast_toggle(struct net_bridge *br, unsigned long val)