[BRIDGE]: fix for RCU and deadlock on device removal

Change Bridge receive path to correctly handle RCU removal of device
from bridge.  Also fixes deadlock between carrier_check and del_nbp.
This replaces the previous deleted flag fix.
Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/bridge/br_if.c

@@ -79,9 +79,14 @@ static int port_cost(struct net_device *dev)
  */
 static void port_carrier_check(void *arg)
 {
-	struct net_bridge_port *p = arg;
+	struct net_device *dev = arg;
+	struct net_bridge_port *p;
 
 	rtnl_lock();
+	p = dev->br_port;
+	if (!p)
+		goto done;
+
 	if (netif_carrier_ok(p->dev)) {
 		u32 cost = port_cost(p->dev);
 
@@ -97,6 +102,7 @@ static void port_carrier_check(void *arg)
 			br_stp_disable_port(p);
 		spin_unlock_bh(&p->br->lock);
 	}
+done:
 	rtnl_unlock();
 }
 
@@ -104,7 +110,6 @@ static void destroy_nbp(struct net_bridge_port *p)
 {
 	struct net_device *dev = p->dev;
 
-	dev->br_port = NULL;
 	p->br = NULL;
 	p->dev = NULL;
 	dev_put(dev);
@@ -133,24 +138,20 @@ static void del_nbp(struct net_bridge_port *p)
 	struct net_bridge *br = p->br;
 	struct net_device *dev = p->dev;
 
-	/* Race between RTNL notify and RCU callback */
-	if (p->deleted)
-		return;
-
 	dev_set_promiscuity(dev, -1);
 
 	cancel_delayed_work(&p->carrier_check);
-	flush_scheduled_work();
 
 	spin_lock_bh(&br->lock);
 	br_stp_disable_port(p);
-	p->deleted = 1;
 	spin_unlock_bh(&br->lock);
 
 	br_fdb_delete_by_port(br, p);
 
 	list_del_rcu(&p->list);
 
+	rcu_assign_pointer(dev->br_port, NULL);
+
 	call_rcu(&p->rcu, destroy_nbp_rcu);
 }
 
@@ -254,11 +255,10 @@ static struct net_bridge_port *new_nbp(struct net_bridge *br,
 	p->dev = dev;
 	p->path_cost = port_cost(dev);
  	p->priority = 0x8000 >> BR_PORT_BITS;
-	dev->br_port = p;
 	p->port_no = index;
 	br_init_port(p);
 	p->state = BR_STATE_DISABLED;
-	INIT_WORK(&p->carrier_check, port_carrier_check, p);
+	INIT_WORK(&p->carrier_check, port_carrier_check, dev);
 	kobject_init(&p->kobj);
 
 	return p;
@@ -397,6 +397,7 @@ int br_add_if(struct net_bridge *br, struct net_device *dev)
 	else if ((err = br_sysfs_addif(p)))
 		del_nbp(p);
 	else {
+		rcu_assign_pointer(dev->br_port, p);
 		dev_set_promiscuity(dev, 1);
 
 		list_add_rcu(&p->list, &br->port_list);

net/bridge/br_input.c

@@ -45,18 +45,20 @@ static void br_pass_frame_up(struct net_bridge *br, struct sk_buff *skb)
 int br_handle_frame_finish(struct sk_buff *skb)
 {
 	const unsigned char *dest = eth_hdr(skb)->h_dest;
-	struct net_bridge_port *p = skb->dev->br_port;
-	struct net_bridge *br = p->br;
+	struct net_bridge_port *p = rcu_dereference(skb->dev->br_port);
+	struct net_bridge *br;
 	struct net_bridge_fdb_entry *dst;
 	int passedup = 0;
 
+	if (!p || p->state == BR_STATE_DISABLED)
+		goto drop;
+
 	/* insert into forwarding database after filtering to avoid spoofing */
-	br_fdb_update(p->br, p, eth_hdr(skb)->h_source);
+	br = p->br;
+	br_fdb_update(br, p, eth_hdr(skb)->h_source);
 
-	if (p->state == BR_STATE_LEARNING) {
-		kfree_skb(skb);
-		goto out;
-	}
+	if (p->state == BR_STATE_LEARNING)
+		goto drop;
 
 	if (br->dev->flags & IFF_PROMISC) {
 		struct sk_buff *skb2;
@@ -93,6 +95,9 @@ int br_handle_frame_finish(struct sk_buff *skb)
 
 out:
 	return 0;
+drop:
+	kfree_skb(skb);
+	goto out;
 }
 
 /*

net/bridge/br_private.h

@@ -68,7 +68,6 @@ struct net_bridge_port
 	/* STP */
 	u8				priority;
 	u8				state;
-	u8				deleted;
 	u16				port_no;
 	unsigned char			topology_change_ack;
 	unsigned char			config_pending;

net/bridge/br_stp_bpdu.c

@@ -133,29 +133,35 @@ void br_send_tcn_bpdu(struct net_bridge_port *p)
 
 static const unsigned char header[6] = {0x42, 0x42, 0x03, 0x00, 0x00, 0x00};
 
-/* NO locks */
+/* NO locks, but rcu_read_lock (preempt_disabled)  */
 int br_stp_handle_bpdu(struct sk_buff *skb)
 {
-	struct net_bridge_port *p = skb->dev->br_port;
-	struct net_bridge *br = p->br;
+	struct net_bridge_port *p = rcu_dereference(skb->dev->br_port);
+	struct net_bridge *br;
 	unsigned char *buf;
 
+	if (!p)
+		goto err;
+
+	br = p->br;
+	spin_lock(&br->lock);
+
+	if (p->state == BR_STATE_DISABLED || !(br->dev->flags & IFF_UP))
+		goto out;
+
 	/* insert into forwarding database after filtering to avoid spoofing */
-	br_fdb_update(p->br, p, eth_hdr(skb)->h_source);
+	br_fdb_update(br, p, eth_hdr(skb)->h_source);
+
+	if (!br->stp_enabled)
+		goto out;
 
 	/* need at least the 802 and STP headers */
 	if (!pskb_may_pull(skb, sizeof(header)+1) ||
 	    memcmp(skb->data, header, sizeof(header)))
-		goto err;
+		goto out;
 
 	buf = skb_pull(skb, sizeof(header));
 
-	spin_lock_bh(&br->lock);
-	if (p->state == BR_STATE_DISABLED 
-	    || !(br->dev->flags & IFF_UP)
-	    || !br->stp_enabled)
-		goto out;
-
 	if (buf[0] == BPDU_TYPE_CONFIG) {
 		struct br_config_bpdu bpdu;
 
@@ -201,7 +207,7 @@ int br_stp_handle_bpdu(struct sk_buff *skb)
 		br_received_tcn_bpdu(p);
 	}
  out:
-	spin_unlock_bh(&br->lock);
+	spin_unlock(&br->lock);
  err:
 	kfree_skb(skb);
 	return 0;