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bonding: fix a div error caused by the slave release path 

There's a bug in the slave release function which leads the transmit
functions which use the bond->slave_cnt to a div by 0 because we might
just have released our last slave and made slave_cnt == 0 but at the same
time we may have a transmitter after the check for an empty list which will
fetch it and use it in the slave id calculation.
Fix it by moving the slave_cnt after synchronize_rcu so if this was our
last slave any new transmitters will see an empty slave list which is
checked after rcu lock but before calling the mode transmit functions
which rely on bond->slave_cnt.

Fixes: 278b208375 ("bonding: initial RCU conversion")

CC: Veaceslav Falico <vfalico@redhat.com>
CC: Andy Gospodarek <andy@greyhouse.net>
CC: Jay Vosburgh <fubar@us.ibm.com>
CC: David S. Miller <davem@davemloft.net>

Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
Acked-by: Veaceslav Falico <vfalico@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Nikolay Aleksandrov 2014-02-26 14:20:30 +01:00 committed by David S. Miller
parent e5fe0cd442
commit ee6154e11e
1 changed files with 1 additions and 3 deletions
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4
drivers/net/bonding/bond_main.c
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@ -1659,9 +1659,6 @@ static int __bond_release_one(struct net_device *bond_dev,
return -EINVAL;
}
/* release the slave from its bond */
bond->slave_cnt--;
bond_sysfs_slave_del(slave);
bond_upper_dev_unlink(bond_dev, slave_dev);
@ -1743,6 +1740,7 @@ static int __bond_release_one(struct net_device *bond_dev,
unblock_netpoll_tx();
synchronize_rcu();
bond->slave_cnt--;
if (!bond_has_slaves(bond)) {
call_netdevice_notifiers(NETDEV_CHANGEADDR, bond->dev);