net: prevent of emerging cross-namespace symlinks

Code manipulating sysfs symlinks on adjacent net_devices(s)
currently doesn't take into account that devices potentially
belong to different namespaces.

This patch trying to fix an issue as follows:
- check for net_ns before creating / deleting symlink.
  for now only netdev_adjacent_rename_links and
  __netdev_adjacent_dev_remove are affected, afaics
  __netdev_adjacent_dev_insert implies both net_devs
  belong to the same namespace.
- Drop all existing symlinks to / from all adj_devs before
  switching namespace and recreate them just after.

Signed-off-by: Alexander Y. Fomichev <git.user@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 60 insertions, 1 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index b65a5051361f..66738e9d66e4 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4889,7 +4889,8 @@ static void __netdev_adjacent_dev_remove(struct net_device *dev,
         if (adj->master)
                 sysfs_remove_link(&(dev->dev.kobj), "master");
 
-        if (netdev_adjacent_is_neigh_list(dev, dev_list))
+        if (netdev_adjacent_is_neigh_list(dev, dev_list) &&
+            net_eq(dev_net(dev),dev_net(adj_dev)))
                 netdev_adjacent_sysfs_del(dev, adj_dev->name, dev_list);
 
         list_del_rcu(&adj->list);
@@ -5159,11 +5160,65 @@ void netdev_upper_dev_unlink(struct net_device *dev,
 }
 EXPORT_SYMBOL(netdev_upper_dev_unlink);
 
+void netdev_adjacent_add_links(struct net_device *dev)
+{
+        struct netdev_adjacent *iter;
+
+        struct net *net = dev_net(dev);
+
+        list_for_each_entry(iter, &dev->adj_list.upper, list) {
+                if (!net_eq(net,dev_net(iter->dev)))
+                        continue;
+                netdev_adjacent_sysfs_add(iter->dev, dev,
+                                          &iter->dev->adj_list.lower);
+                netdev_adjacent_sysfs_add(dev, iter->dev,
+                                          &dev->adj_list.upper);
+        }
+
+        list_for_each_entry(iter, &dev->adj_list.lower, list) {
+                if (!net_eq(net,dev_net(iter->dev)))
+                        continue;
+                netdev_adjacent_sysfs_add(iter->dev, dev,
+                                          &iter->dev->adj_list.upper);
+                netdev_adjacent_sysfs_add(dev, iter->dev,
+                                          &dev->adj_list.lower);
+        }
+}
+
+void netdev_adjacent_del_links(struct net_device *dev)
+{
+        struct netdev_adjacent *iter;
+
+        struct net *net = dev_net(dev);
+
+        list_for_each_entry(iter, &dev->adj_list.upper, list) {
+                if (!net_eq(net,dev_net(iter->dev)))
+                        continue;
+                netdev_adjacent_sysfs_del(iter->dev, dev->name,
+                                          &iter->dev->adj_list.lower);
+                netdev_adjacent_sysfs_del(dev, iter->dev->name,
+                                          &dev->adj_list.upper);
+        }
+
+        list_for_each_entry(iter, &dev->adj_list.lower, list) {
+                if (!net_eq(net,dev_net(iter->dev)))
+                        continue;
+                netdev_adjacent_sysfs_del(iter->dev, dev->name,
+                                          &iter->dev->adj_list.upper);
+                netdev_adjacent_sysfs_del(dev, iter->dev->name,
+                                          &dev->adj_list.lower);
+        }
+}
+
 void netdev_adjacent_rename_links(struct net_device *dev, char *oldname)
 {
         struct netdev_adjacent *iter;
 
+        struct net *net = dev_net(dev);
+
         list_for_each_entry(iter, &dev->adj_list.upper, list) {
+                if (!net_eq(net,dev_net(iter->dev)))
+                        continue;
                 netdev_adjacent_sysfs_del(iter->dev, oldname,
                                           &iter->dev->adj_list.lower);
                 netdev_adjacent_sysfs_add(iter->dev, dev,
@@ -5171,6 +5226,8 @@ void netdev_adjacent_rename_links(struct net_device *dev, char *oldname)
         }
 
         list_for_each_entry(iter, &dev->adj_list.lower, list) {
+                if (!net_eq(net,dev_net(iter->dev)))
+                        continue;
                 netdev_adjacent_sysfs_del(iter->dev, oldname,
                                           &iter->dev->adj_list.upper);
                 netdev_adjacent_sysfs_add(iter->dev, dev,
@@ -6773,6 +6830,7 @@ int dev_change_net_namespace(struct net_device *dev, struct net *net, const char
 
         /* Send a netdev-removed uevent to the old namespace */
         kobject_uevent(&dev->dev.kobj, KOBJ_REMOVE);
+        netdev_adjacent_del_links(dev);
 
         /* Actually switch the network namespace */
         dev_net_set(dev, net);
@@ -6787,6 +6845,7 @@ int dev_change_net_namespace(struct net_device *dev, struct net *net, const char
 
         /* Send a netdev-add uevent to the new namespace */
         kobject_uevent(&dev->dev.kobj, KOBJ_ADD);
+        netdev_adjacent_add_links(dev);
 
         /* Fixup kobjects */
         err = device_rename(&dev->dev, dev->name);