vlan: Fix vlan-in-vlan crashes.

As analyzed by Patrick McHardy, vlan needs to reset it's
netdev_ops pointer in it's ->init() function but this
leaves the compat method pointers stale.

Add a netdev_resync_ops() and call it from the vlan code.

Any other driver which changes ->netdev_ops after register_netdevice()
will need to call this new function after doing so too.

With help from Patrick McHardy.

Tested-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 37 insertions, 23 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index ec54785d34f9..659366734f3f 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1079,6 +1079,7 @@ extern void		synchronize_net(void);
 extern int              register_netdevice_notifier(struct notifier_block *nb);
 extern int              unregister_netdevice_notifier(struct notifier_block *nb);
 extern int              init_dummy_netdev(struct net_device *dev);
+extern void             netdev_resync_ops(struct net_device *dev);
 
 extern int call_netdevice_notifiers(unsigned long val, struct net_device *dev);
 extern struct net_device        *dev_get_by_index(struct net *net, int ifindex);
diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
index 4a19acd3a32b..1b34135cf990 100644
--- a/net/8021q/vlan_dev.c
+++ b/net/8021q/vlan_dev.c
@@ -553,7 +553,7 @@ static int vlan_dev_neigh_setup(struct net_device *dev, struct neigh_parms *pa)
         int err = 0;
 
         if (netif_device_present(real_dev) && ops->ndo_neigh_setup)
-                err = ops->ndo_neigh_setup(dev, pa);
+                err = ops->ndo_neigh_setup(real_dev, pa);
 
         return err;
 }
@@ -639,6 +639,7 @@ static int vlan_dev_init(struct net_device *dev)
                 dev->hard_header_len = real_dev->hard_header_len + VLAN_HLEN;
                 dev->netdev_ops         = &vlan_netdev_ops;
         }
+        netdev_resync_ops(dev);
 
         if (is_vlan_dev(real_dev))
                 subclass = 1;
diff --git a/net/core/dev.c b/net/core/dev.c
index 2dd484ed3dbb..f1129706ce7b 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4282,6 +4282,39 @@ unsigned long netdev_fix_features(unsigned long features, const char *name)
 }
 EXPORT_SYMBOL(netdev_fix_features);
 
+/* Some devices need to (re-)set their netdev_ops inside
+ * ->init() or similar.  If that happens, we have to setup
+ * the compat pointers again.
+ */
+void netdev_resync_ops(struct net_device *dev)
+{
+#ifdef CONFIG_COMPAT_NET_DEV_OPS
+        const struct net_device_ops *ops = dev->netdev_ops;
+
+        dev->init = ops->ndo_init;
+        dev->uninit = ops->ndo_uninit;
+        dev->open = ops->ndo_open;
+        dev->change_rx_flags = ops->ndo_change_rx_flags;
+        dev->set_rx_mode = ops->ndo_set_rx_mode;
+        dev->set_multicast_list = ops->ndo_set_multicast_list;
+        dev->set_mac_address = ops->ndo_set_mac_address;
+        dev->validate_addr = ops->ndo_validate_addr;
+        dev->do_ioctl = ops->ndo_do_ioctl;
+        dev->set_config = ops->ndo_set_config;
+        dev->change_mtu = ops->ndo_change_mtu;
+        dev->neigh_setup = ops->ndo_neigh_setup;
+        dev->tx_timeout = ops->ndo_tx_timeout;
+        dev->get_stats = ops->ndo_get_stats;
+        dev->vlan_rx_register = ops->ndo_vlan_rx_register;
+        dev->vlan_rx_add_vid = ops->ndo_vlan_rx_add_vid;
+        dev->vlan_rx_kill_vid = ops->ndo_vlan_rx_kill_vid;
+#ifdef CONFIG_NET_POLL_CONTROLLER
+        dev->poll_controller = ops->ndo_poll_controller;
+#endif
+#endif
+}
+EXPORT_SYMBOL(netdev_resync_ops);
+
 /**
  *      register_netdevice      - register a network device
  *      @dev: device to register
@@ -4326,28 +4359,7 @@ int register_netdevice(struct net_device *dev)
          * This is temporary until all network devices are converted.
          */
         if (dev->netdev_ops) {
-                const struct net_device_ops *ops = dev->netdev_ops;
-
-                dev->init = ops->ndo_init;
-                dev->uninit = ops->ndo_uninit;
-                dev->open = ops->ndo_open;
-                dev->change_rx_flags = ops->ndo_change_rx_flags;
-                dev->set_rx_mode = ops->ndo_set_rx_mode;
-                dev->set_multicast_list = ops->ndo_set_multicast_list;
-                dev->set_mac_address = ops->ndo_set_mac_address;
-                dev->validate_addr = ops->ndo_validate_addr;
-                dev->do_ioctl = ops->ndo_do_ioctl;
-                dev->set_config = ops->ndo_set_config;
-                dev->change_mtu = ops->ndo_change_mtu;
-                dev->neigh_setup = ops->ndo_neigh_setup;
-                dev->tx_timeout = ops->ndo_tx_timeout;
-                dev->get_stats = ops->ndo_get_stats;
-                dev->vlan_rx_register = ops->ndo_vlan_rx_register;
-                dev->vlan_rx_add_vid = ops->ndo_vlan_rx_add_vid;
-                dev->vlan_rx_kill_vid = ops->ndo_vlan_rx_kill_vid;
-#ifdef CONFIG_NET_POLL_CONTROLLER
-                dev->poll_controller = ops->ndo_poll_controller;
-#endif
+                netdev_resync_ops(dev);
         } else {
                 char drivername[64];
                 pr_info("%s (%s): not using net_device_ops yet\n",