Subject: [PATCH 05/43] net: bridge: multicast: use rcu to access port list from br_multicast_start_querier

From: Nikolay Aleksandrov <[email-masked]>
Date: Thu, 11 Apr 2019 15:08:25 +0300

[ 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 <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 net/bridge/br_multicast.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index e4777614a8a0..61ff0d497da6 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -1916,7 +1916,8 @@ static void br_multicast_start_querier(struct net_bridge *br,
 
 	__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;
@@ -1928,6 +1929,7 @@ static void br_multicast_start_querier(struct net_bridge *br,
 			br_multicast_enable(&port->ip6_own_query);
 #endif
 	}
+	rcu_read_unlock();
 }
 
 int br_multicast_toggle(struct net_bridge *br, unsigned long val)
-- 
2.20.1