[Devel] [PATCH RH7 1/3] net: prevent of emerging cross-namespace symlinks

[Pavel Tikhomirov]

From: "Alexander Y. Fomichev" <git.user at gmail.com>

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.

https://jira.sw.ru/browse/PSBM-58300

Signed-off-by: Alexander Y. Fomichev <git.user at gmail.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
---
 net/core/dev.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 60 insertions(+), 1 deletion(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index e7c21ea..b1a183d 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5267,7 +5267,8 @@ 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);
@@ -5573,11 +5574,65 @@ void netdev_bonding_info_change(struct net_device *dev,
 }
 EXPORT_SYMBOL(netdev_bonding_info_change);
 
+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,
@@ -5585,6 +5640,8 @@ 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,
@@ -7388,6 +7445,7 @@ 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);
@@ -7402,6 +7460,7 @@ 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);
-- 
2.9.3