softmac: Fix deadlock of wx_set_essid with assoc work

The essid wireless extension does deadlock against the assoc mutex,
as we don't unlock the assoc mutex when flushing the workqueue, which
also holds the lock.
Signed-off-by: Michael Buesch <mb@bu3sch.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

net/ieee80211/softmac/ieee80211softmac_wx.c

@@ -74,8 +74,8 @@ ieee80211softmac_wx_set_essid(struct net_device *net_dev,
 	struct ieee80211softmac_auth_queue_item *authptr;
 	int length = 0;
 
+check_assoc_again:
 	mutex_lock(&sm->associnfo.mutex);
-
 	/* Check if we're already associating to this or another network
 	 * If it's another network, cancel and start over with our new network
 	 * If it's our network, ignore the change, we're already doing it!
@@ -98,13 +98,18 @@ ieee80211softmac_wx_set_essid(struct net_device *net_dev,
 				cancel_delayed_work(&authptr->work);
 			sm->associnfo.bssvalid = 0;
 			sm->associnfo.bssfixed = 0;
-			flush_scheduled_work();
 			sm->associnfo.associating = 0;
 			sm->associnfo.associated = 0;
+			/* We must unlock to avoid deadlocks with the assoc workqueue
+			 * on the associnfo.mutex */
+			mutex_unlock(&sm->associnfo.mutex);
+			flush_scheduled_work();
+			/* Avoid race! Check assoc status again. Maybe someone started an
+			 * association while we flushed. */
+			goto check_assoc_again;
 		}
 	}
 
-
 	sm->associnfo.static_essid = 0;
 	sm->associnfo.assoc_wait = 0;