uml: network interface hotplug error handling

This fixes a number of problems associated with network interface hotplug.

The userspace initialization function can fail in some cases, but the
failure was never passed back to eth_configure, which proceeded with the
configuration.  This results in a zombie device that is present, but can't
work.  This is fixed by allowing the initialization routines to return an
error, which is checked, and the configuration aborted on failure.

eth_configure failed to check for many failures.  Even when it did check,
it didn't undo whatever initializations has already happened, so a present,
but partially initialized and non-working device could result.  It now
checks everything that can fail, and bails out, undoing whatever had been
done.

The return value of eth_configure was always ignored, so it is now just
void.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 46 insertions, 35 deletions

diff --git a/arch/um/drivers/net_kern.c b/arch/um/drivers/net_kern.c
index 859303730b2f..ac746fb5d10f 100644
--- a/arch/um/drivers/net_kern.c
+++ b/arch/um/drivers/net_kern.c
@@ -325,8 +325,8 @@ static struct platform_driver uml_net_driver = {
 };
 static int driver_registered;
 
-static int eth_configure(int n, void *init, char *mac,
-                         struct transport *transport)
+static void eth_configure(int n, void *init, char *mac,
+                          struct transport *transport)
 {
         struct uml_net *device;
         struct net_device *dev;
@@ -339,16 +339,12 @@ static int eth_configure(int n, void *init, char *mac,
         device = kzalloc(sizeof(*device), GFP_KERNEL);
         if (device == NULL) {
                 printk(KERN_ERR "eth_configure failed to allocate uml_net\n");
-                return(1);
+                return;
         }
 
         INIT_LIST_HEAD(&device->list);
         device->index = n;
 
-        spin_lock(&devices_lock);
-        list_add(&device->list, &devices);
-        spin_unlock(&devices_lock);
-
         setup_etheraddr(mac, device->mac);
 
         printk(KERN_INFO "Netdevice %d ", n);
@@ -360,7 +356,7 @@ static int eth_configure(int n, void *init, char *mac,
         dev = alloc_etherdev(size);
         if (dev == NULL) {
                 printk(KERN_ERR "eth_configure: failed to allocate device\n");
-                return 1;
+                goto out_free_device;
         }
 
         lp = dev->priv;
@@ -376,7 +372,8 @@ static int eth_configure(int n, void *init, char *mac,
         }
         device->pdev.id = n;
         device->pdev.name = DRIVER_NAME;
-        platform_device_register(&device->pdev);
+        if(platform_device_register(&device->pdev))
+                goto out_free_netdev;
         SET_NETDEV_DEV(dev,&device->pdev.dev);
 
         /* If this name ends up conflicting with an existing registered
@@ -386,31 +383,12 @@ static int eth_configure(int n, void *init, char *mac,
         snprintf(dev->name, sizeof(dev->name), "eth%d", n);
         device->dev = dev;
 
+        /*
+         * These just fill in a data structure, so there's no failure
+         * to be worried about.
+         */
         (*transport->kern->init)(dev, init);
 
-        dev->mtu = transport->user->max_packet;
-        dev->open = uml_net_open;
-        dev->hard_start_xmit = uml_net_start_xmit;
-        dev->stop = uml_net_close;
-        dev->get_stats = uml_net_get_stats;
-        dev->set_multicast_list = uml_net_set_multicast_list;
-        dev->tx_timeout = uml_net_tx_timeout;
-        dev->set_mac_address = uml_net_set_mac;
-        dev->change_mtu = uml_net_change_mtu;
-        dev->ethtool_ops = &uml_net_ethtool_ops;
-        dev->watchdog_timeo = (HZ >> 1);
-        dev->irq = UM_ETH_IRQ;
-
-        rtnl_lock();
-        err = register_netdevice(dev);
-        rtnl_unlock();
-        if (err) {
-                device->dev = NULL;
-                /* XXX: should we call ->remove() here? */
-                free_netdev(dev);
-                return 1;
-        }
-
         /* lp.user is the first four bytes of the transport data, which
          * has already been initialized.  This structure assignment will
          * overwrite that, so we make sure that .user gets overwritten with
@@ -438,12 +416,45 @@ static int eth_configure(int n, void *init, char *mac,
         lp->tl.function = uml_net_user_timer_expire;
         memcpy(lp->mac, device->mac, sizeof(lp->mac));
 
-        if (transport->user->init)
-                (*transport->user->init)(&lp->user, dev);
+        if ((transport->user->init != NULL) &&
+            ((*transport->user->init)(&lp->user, dev) != 0))
+                goto out_unregister;
 
         set_ether_mac(dev, device->mac);
+        dev->mtu = transport->user->max_packet;
+        dev->open = uml_net_open;
+        dev->hard_start_xmit = uml_net_start_xmit;
+        dev->stop = uml_net_close;
+        dev->get_stats = uml_net_get_stats;
+        dev->set_multicast_list = uml_net_set_multicast_list;
+        dev->tx_timeout = uml_net_tx_timeout;
+        dev->set_mac_address = uml_net_set_mac;
+        dev->change_mtu = uml_net_change_mtu;
+        dev->ethtool_ops = &uml_net_ethtool_ops;
+        dev->watchdog_timeo = (HZ >> 1);
+        dev->irq = UM_ETH_IRQ;
 
-        return 0;
+        rtnl_lock();
+        err = register_netdevice(dev);
+        rtnl_unlock();
+        if (err)
+                goto out_undo_user_init;
+
+        spin_lock(&devices_lock);
+        list_add(&device->list, &devices);
+        spin_unlock(&devices_lock);
+
+        return;
+
+out_undo_user_init:
+        if (transport->user->init != NULL)
+                (*transport->user->remove)(&lp->user);
+out_unregister:
+        platform_device_unregister(&device->pdev);
+out_free_netdev:
+        free_netdev(dev);
+out_free_device: ;
+        kfree(device);
 }
 
 static struct uml_net *find_device(int n)