net: dsa: Ensure that port array elements are initialized before being used

A network device notifier can be called for one or more of the created
slave devices before all slave devices have been registered. This can
result in a mismatch between ds->phys_port_mask and the registered devices
by the time the call is made, and it can result in a slave device being
added to a bridge before its entry in ds->ports[] has been initialized.

Rework the initialization code to initialize entries in ds->ports[] in
dsa_slave_create. With this change, dsa_slave_create no longer needs
to return slave_dev but can return an error code instead.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dsa/dsa.c

@@ -314,19 +314,15 @@ dsa_switch_setup(struct dsa_switch_tree *dst, int index,
 	 * Create network devices for physical switch ports.
 	 */
 	for (i = 0; i < DSA_MAX_PORTS; i++) {
-		struct net_device *slave_dev;
-
 		if (!(ds->phys_port_mask & (1 << i)))
 			continue;
 
-		slave_dev = dsa_slave_create(ds, parent, i, pd->port_names[i]);
-		if (slave_dev == NULL) {
+		ret = dsa_slave_create(ds, parent, i, pd->port_names[i]);
+		if (ret < 0) {
 			netdev_err(dst->master_netdev, "[%d]: can't create dsa slave device for port %d(%s)\n",
 				   index, i, pd->port_names[i]);
-			continue;
+			ret = 0;
 		}
-
-		ds->ports[i] = slave_dev;
 	}
 
 #ifdef CONFIG_NET_DSA_HWMON

net/dsa/dsa_priv.h

@@ -53,9 +53,8 @@ extern char dsa_driver_version[];
 /* slave.c */
 extern const struct dsa_device_ops notag_netdev_ops;
 void dsa_slave_mii_bus_init(struct dsa_switch *ds);
-struct net_device *dsa_slave_create(struct dsa_switch *ds,
-				    struct device *parent,
-				    int port, char *name);
+int dsa_slave_create(struct dsa_switch *ds, struct device *parent,
+		     int port, char *name);
 int dsa_slave_suspend(struct net_device *slave_dev);
 int dsa_slave_resume(struct net_device *slave_dev);
 

net/dsa/slave.c

@@ -605,9 +605,8 @@ int dsa_slave_resume(struct net_device *slave_dev)
 	return 0;
 }
 
-struct net_device *
-dsa_slave_create(struct dsa_switch *ds, struct device *parent,
-		 int port, char *name)
+int dsa_slave_create(struct dsa_switch *ds, struct device *parent,
+		     int port, char *name)
 {
 	struct net_device *master = ds->dst->master_netdev;
 	struct net_device *slave_dev;
@@ -617,7 +616,7 @@ dsa_slave_create(struct dsa_switch *ds, struct device *parent,
 	slave_dev = alloc_netdev(sizeof(struct dsa_slave_priv), name,
 				 NET_NAME_UNKNOWN, ether_setup);
 	if (slave_dev == NULL)
-		return slave_dev;
+		return -ENOMEM;
 
 	slave_dev->features = master->vlan_features;
 	slave_dev->ethtool_ops = &dsa_slave_ethtool_ops;
@@ -667,19 +666,21 @@ dsa_slave_create(struct dsa_switch *ds, struct device *parent,
 	ret = dsa_slave_phy_setup(p, slave_dev);
 	if (ret) {
 		free_netdev(slave_dev);
-		return NULL;
+		return ret;
 	}
 
+	ds->ports[port] = slave_dev;
 	ret = register_netdev(slave_dev);
 	if (ret) {
 		netdev_err(master, "error %d registering interface %s\n",
 			   ret, slave_dev->name);
 		phy_disconnect(p->phy);
+		ds->ports[port] = NULL;
 		free_netdev(slave_dev);
-		return NULL;
+		return ret;
 	}
 
 	netif_carrier_off(slave_dev);
 
-	return slave_dev;
+	return 0;
 }