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IB/sa_query: Fix AH leak due to update_sm_ah() race 

Our testing uncovered a race condition in ib_sa_event():

	spin_lock_irqsave(&port->ah_lock, flags);
	if (port->sm_ah)
		kref_put(&port->sm_ah->ref, free_sm_ah);
	port->sm_ah = NULL;
	spin_unlock_irqrestore(&port->ah_lock, flags);

	schedule_work(&sa_dev->port[event->element.port_num -
				    sa_dev->start_port].update_task);

If two events occur back-to-back (e.g., client-reregister and LID
change), both may pass the spinlock-protected code above before the
scheduled work updates the port->sm_ah handle.  Then if the scheduled
work ends up running twice, the second operation will then find a
non-NULL port->sm_ah, and will simply overwrite it in update_sm_ah --
resulting in an AH leak.

Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
This commit is contained in:
Jack Morgenstein 2009-03-03 14:30:01 -08:00 committed by Roland Dreier
parent f3b8436ad9
commit 6b708b3dde
1 changed files with 2 additions and 0 deletions
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2
drivers/infiniband/core/sa_query.c
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@ -395,6 +395,8 @@ static void update_sm_ah(struct work_struct *work)
}
spin_lock_irq(&port->ah_lock);
if (port->sm_ah)
kref_put(&port->sm_ah->ref, free_sm_ah);
port->sm_ah = new_ah;
spin_unlock_irq(&port->ah_lock);