bonding: fix a race in IGMP handling

RCU conversion in IGMP code done in net-next-2.6 raised a race in
__bond_resend_igmp_join_requests().

It iterates in_dev->mc_list without appropriate protection (RTNL, or
read_lock on in_dev->mc_list_lock).

Another cpu might delete an entry while we use it and trigger a fault.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index bdb68a600382..71a169740d05 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -878,8 +878,10 @@ static void __bond_resend_igmp_join_requests(struct net_device *dev)
         rcu_read_lock();
         in_dev = __in_dev_get_rcu(dev);
         if (in_dev) {
+                read_lock(&in_dev->mc_list_lock);
                 for (im = in_dev->mc_list; im; im = im->next)
                         ip_mc_rejoin_group(im);
+                read_unlock(&in_dev->mc_list_lock);
         }
 
         rcu_read_unlock();