bonding: Fix race condition between bond_enslave() and bond_3ad_update_lacp_rate()

port->slave can be NULL since it's being initialized in bond_enslave
thus dereferencing a NULL pointer in bond_3ad_update_lacp_rate()
Also fix a minor bug, which could cause a port not to have
AD_STATE_LACP_TIMEOUT since there's no sync between
bond_3ad_update_lacp_rate() and bond_3ad_bind_slave(), by changing
the read_lock to a write_lock_bh in bond_3ad_update_lacp_rate().

Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 2 deletions

diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c
index 84fabd69df4c..0e45b400b6fc 100644
--- a/drivers/net/bonding/bond_3ad.c
+++ b/drivers/net/bonding/bond_3ad.c
@@ -2494,11 +2494,13 @@ void bond_3ad_update_lacp_rate(struct bonding *bond)
         struct port *port = NULL;
         int lacp_fast;
 
-        read_lock(&bond->lock);
+        write_lock_bh(&bond->lock);
         lacp_fast = bond->params.lacp_fast;
 
         bond_for_each_slave(bond, slave, i) {
                 port = &(SLAVE_AD_INFO(slave).port);
+                if (port->slave == NULL)
+                        continue;
                 __get_state_machine_lock(port);
                 if (lacp_fast)
                         port->actor_oper_port_state |= AD_STATE_LACP_TIMEOUT;
@@ -2507,5 +2509,5 @@ void bond_3ad_update_lacp_rate(struct bonding *bond)
                 __release_state_machine_lock(port);
         }
 
-        read_unlock(&bond->lock);
+        write_unlock_bh(&bond->lock);
 }