[PATCH 3.12 04/83] bonding: RCUify bond_set_rx_mode()

[Greg Kroah-Hartman]

3.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Veaceslav Falico <vfalico@xxxxxxxxxx>

[ Upstream commit b32418705107265dfca5edfe2b547643e53a732e ]

Currently we rely on rtnl locking in bond_set_rx_mode(), however it's not
always the case:

RTNL: assertion failed at drivers/net/bonding/bond_main.c (3391)
...
 [<ffffffff81651ca5>] dump_stack+0x54/0x74
 [<ffffffffa029e717>] bond_set_rx_mode+0xc7/0xd0 [bonding]
 [<ffffffff81553af7>] __dev_set_rx_mode+0x57/0xa0
 [<ffffffff81557ff8>] __dev_mc_add+0x58/0x70
 [<ffffffff81558020>] dev_mc_add+0x10/0x20
 [<ffffffff8161e26e>] igmp6_group_added+0x18e/0x1d0
 [<ffffffff81186f76>] ? kmem_cache_alloc_trace+0x236/0x260
 [<ffffffff8161f80f>] ipv6_dev_mc_inc+0x29f/0x320
 [<ffffffff8161f9e7>] ipv6_sock_mc_join+0x157/0x260
...

Fix this by using RCU primitives.

Reported-by: Joe Lawrence <joe.lawrence@xxxxxxxxxxx>
Tested-by: Joe Lawrence <joe.lawrence@xxxxxxxxxxx>
CC: Jay Vosburgh <fubar@xxxxxxxxxx>
CC: Andy Gospodarek <andy@xxxxxxxxxxxxx>
Signed-off-by: Veaceslav Falico <vfalico@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/net/bonding/bond_main.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -3395,20 +3395,20 @@ static void bond_set_rx_mode(struct net_
 	struct bonding *bond = netdev_priv(bond_dev);
 	struct slave *slave;
 
-	ASSERT_RTNL();
-
+	rcu_read_lock();
 	if (USES_PRIMARY(bond->params.mode)) {
-		slave = rtnl_dereference(bond->curr_active_slave);
+		slave = rcu_dereference(bond->curr_active_slave);
 		if (slave) {
 			dev_uc_sync(slave->dev, bond_dev);
 			dev_mc_sync(slave->dev, bond_dev);
 		}
 	} else {
-		bond_for_each_slave(bond, slave) {
+		bond_for_each_slave_rcu(bond, slave) {
 			dev_uc_sync_multiple(slave->dev, bond_dev);
 			dev_mc_sync_multiple(slave->dev, bond_dev);
 		}
 	}
+	rcu_read_unlock();
 }
 
 static int bond_neigh_init(struct neighbour *n)


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