net: fix removing a namespace with conflicting altnames

[ Upstream commit d09486a04f5da0a812c26217213b89a3b1acf836 ]

Mark reports a BUG() when a net namespace is removed.

    kernel BUG at net/core/dev.c:11520!

Physical interfaces moved outside of init_net get "refunded"
to init_net when that namespace disappears. The main interface
name may get overwritten in the process if it would have
conflicted. We need to also discard all conflicting altnames.
Recent fixes addressed ensuring that altnames get moved
with the main interface, which surfaced this problem.

Reported-by: Марк Коренберг <socketpair@gmail.com>
Link: https://lore.kernel.org/all/CAEmTpZFZ4Sv3KwqFOY2WKDHeZYdi0O7N5H1nTvcGp=SAEavtDg@mail.gmail.com/
Fixes: 7663d522099e ("net: check for altname conflicts when changing netdev's netns")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Reviewed-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/core/dev.c b/net/core/dev.c
index e480afb..d72a4ff 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -11491,6 +11491,7 @@ static struct pernet_operations __net_initdata netdev_net_ops = {
 
 static void __net_exit default_device_exit_net(struct net *net)
 {
+       struct netdev_name_node *name_node, *tmp;
        struct net_device *dev, *aux;
        /*
         * Push all migratable network devices back to the
@@ -11513,6 +11514,14 @@ static void __net_exit default_device_exit_net(struct net *net)
                snprintf(fb_name, IFNAMSIZ, "dev%d", dev->ifindex);
                if (netdev_name_in_use(&init_net, fb_name))
                        snprintf(fb_name, IFNAMSIZ, "dev%%d");
+
+               netdev_for_each_altname_safe(dev, name_node, tmp)
+                       if (netdev_name_in_use(&init_net, name_node->name)) {
+                               netdev_name_node_del(name_node);
+                               synchronize_rcu();
+                               __netdev_name_node_alt_destroy(name_node);
+                       }
+
                err = dev_change_net_namespace(dev, &init_net, fb_name);
                if (err) {
                        pr_emerg("%s: failed to move %s to init_net: %d\n",

diff --git a/net/core/dev.h b/net/core/dev.h
index fa2e9c5..f2037d4 100644 (file)
--- a/net/core/dev.h
+++ b/net/core/dev.h
@@ -64,6 +64,9 @@ int dev_change_name(struct net_device *dev, const char *newname);
 
 #define netdev_for_each_altname(dev, namenode)                         \
        list_for_each_entry((namenode), &(dev)->name_node->list, list)
+#define netdev_for_each_altname_safe(dev, namenode, next)              \
+       list_for_each_entry_safe((namenode), (next), &(dev)->name_node->list, \
+                                list)
 
 int netdev_name_node_alt_create(struct net_device *dev, const char *name);
 int netdev_name_node_alt_destroy(struct net_device *dev, const char *name);