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[NET]: Fix race in dev_close(). (Bug 9750) 

There is a race in Linux kernel file net/core/dev.c, function dev_close.
The function calls function dev_deactivate, which calls function
dev_watchdog_down that deletes the watchdog timer. However, after that, a
driver can call netif_carrier_ok, which calls function
__netdev_watchdog_up that can add the watchdog timer again. Function
unregister_netdevice calls function dev_shutdown that traps the bug
!timer_pending(&dev->watchdog_timer). Moving dev_deactivate after
netif_running() has been cleared prevents function netif_carrier_on
from calling __netdev_watchdog_up and adding the watchdog timer again.

Signed-off-by: Matti Linnanvuori <mattilinnanvuori@yahoo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Matti Linnanvuori 2008-02-12 23:10:11 -08:00 committed by David S. Miller
parent b318e0e4ef
commit d8b2a4d21e
1 changed files with 2 additions and 2 deletions
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4
net/core/dev.c
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@ -1071,8 +1071,6 @@ int dev_close(struct net_device *dev)
*/
call_netdevice_notifiers(NETDEV_GOING_DOWN, dev);
dev_deactivate(dev);
clear_bit(__LINK_STATE_START, &dev->state);
/* Synchronize to scheduled poll. We cannot touch poll list,
@ -1083,6 +1081,8 @@ int dev_close(struct net_device *dev)
*/
smp_mb__after_clear_bit(); /* Commit netif_running(). */
dev_deactivate(dev);
/*
* Call the device specific close. This cannot fail.
* Only if device is UP