net: openvswitch: fixes potential deadlock in dp cleanup code

The previous patch introduced a deadlock, this patch fixes it by making
sure the work is canceled without holding the global ovs lock. This is
done by moving the reorder processing one layer up to the netns level.

Fixes: eac87c413bf9 ("net: openvswitch: reorder masks array based on usage")
Reported-by: [e-mail]
Reported-by: [e-mail]
Reviewed-by: Paolo <[e-mail]>
Signed-off-by: Eelco Chaudron <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/openvswitch/datapath.c

···
 		goto err_destroy_reply;
 
 	ovs_dp_set_net(dp, sock_net(skb->sk));
-	INIT_DELAYED_WORK(&dp->masks_rebalance, ovs_dp_masks_rebalance);
 
 	/* Allocate table. */
 	err = ovs_flow_tbl_init(&dp->table);
···
 	ovs_net = net_generic(ovs_dp_get_net(dp), ovs_net_id);
 	list_add_tail_rcu(&dp->list_node, &ovs_net->dps);
 
-	schedule_delayed_work(&dp->masks_rebalance,
-			      msecs_to_jiffies(DP_MASKS_REBALANCE_INTERVAL));
-
 	ovs_unlock();
 
 	ovs_notify(&dp_datapath_genl_family, reply, info);
···
 
 	/* RCU destroy the flow table */
 	call_rcu(&dp->rcu, destroy_dp_rcu);
-
-	/* Cancel remaining work. */
-	cancel_delayed_work_sync(&dp->masks_rebalance);
 }
 
 static int ovs_dp_cmd_del(struct sk_buff *skb, struct genl_info *info)
···
 
 static void ovs_dp_masks_rebalance(struct work_struct *work)
 {
-	struct datapath *dp = container_of(work, struct datapath,
-					   masks_rebalance.work);
+	struct ovs_net *ovs_net = container_of(work, struct ovs_net,
+					       masks_rebalance.work);
+	struct datapath *dp;
 
 	ovs_lock();
-	ovs_flow_masks_rebalance(&dp->table);
+
+	list_for_each_entry(dp, &ovs_net->dps, list_node)
+		ovs_flow_masks_rebalance(&dp->table);
+
 	ovs_unlock();
 
-	schedule_delayed_work(&dp->masks_rebalance,
+	schedule_delayed_work(&ovs_net->masks_rebalance,
 			      msecs_to_jiffies(DP_MASKS_REBALANCE_INTERVAL));
 }
 
···
 
 	INIT_LIST_HEAD(&ovs_net->dps);
 	INIT_WORK(&ovs_net->dp_notify_work, ovs_dp_notify_wq);
+	INIT_DELAYED_WORK(&ovs_net->masks_rebalance, ovs_dp_masks_rebalance);
+	schedule_delayed_work(&ovs_net->masks_rebalance,
+			      msecs_to_jiffies(DP_MASKS_REBALANCE_INTERVAL));
 	return ovs_ct_init(net);
 }
 
···
 
 	ovs_unlock();
 
+	cancel_delayed_work_sync(&ovs_net->masks_rebalance);
 	cancel_work_sync(&ovs_net->dp_notify_work);
 }
 

net/openvswitch/datapath.h

···
 
 	/* Switch meters. */
 	struct dp_meter_table meter_tbl;
-
-	/* re-balance flow masks timer */
-	struct delayed_work masks_rebalance;
 };
 
 /**
···
 struct ovs_net {
 	struct list_head dps;
 	struct work_struct dp_notify_work;
+	struct delayed_work masks_rebalance;
 #if	IS_ENABLED(CONFIG_NETFILTER_CONNCOUNT)
 	struct ovs_ct_limit_info *ct_limit_info;
 #endif