[PATCH 3.18 091/104] net: bridge: multicast: use rcu to access port list from br_multicast_start_querier

Greg Kroah-Hartman
2019-04-24T18:09:58Z

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
@@ -2023,7 +2023,8 @@ 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;
@@ -2035,6 +2036,7 @@ 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)