bonding: fix __get_active_agg() RCU logic

Currently, the implementation is meaningless - once again, we take the
slave structure and use it after we've exited RCU critical section.

Fix this by removing the rcu_read_lock() from __get_active_agg(), and
ensuring that all its callers are holding RCU.

Fixes: be79bd048 ("bonding: add RCU for bond_3ad_state_machine_handler()")
CC: dingtianhong@huawei.com
CC: Jay Vosburgh <fubar@us.ibm.com>
CC: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: Veaceslav Falico <vfalico@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c
index b49f421..cce1f1b 100644 (file)
--- a/drivers/net/bonding/bond_3ad.c
+++ b/drivers/net/bonding/bond_3ad.c
@@ -678,6 +678,8 @@ static u32 __get_agg_bandwidth(struct aggregator *aggregator)
 /**
  * __get_active_agg - get the current active aggregator
  * @aggregator: the aggregator we're looking at
+ *
+ * Caller must hold RCU lock.
  */
 static struct aggregator *__get_active_agg(struct aggregator *aggregator)
 {
@@ -685,13 +687,9 @@ static struct aggregator *__get_active_agg(struct aggregator *aggregator)
        struct list_head *iter;
        struct slave *slave;
 
-       rcu_read_lock();
        bond_for_each_slave_rcu(bond, slave, iter)
-               if (SLAVE_AD_INFO(slave).aggregator.is_active) {
-                       rcu_read_unlock();
+               if (SLAVE_AD_INFO(slave).aggregator.is_active)
                        return &(SLAVE_AD_INFO(slave).aggregator);
-               }
-       rcu_read_unlock();
 
        return NULL;
 }
@@ -1499,11 +1497,11 @@ static void ad_agg_selection_logic(struct aggregator *agg)
        struct slave *slave;
        struct port *port;
 
+       rcu_read_lock();
        origin = agg;
        active = __get_active_agg(agg);
        best = (active && agg_device_up(active)) ? active : NULL;
 
-       rcu_read_lock();
        bond_for_each_slave_rcu(bond, slave, iter) {
                agg = &(SLAVE_AD_INFO(slave).aggregator);