Patch "net: fix removing a namespace with conflicting altnames" has been added to the 6.6-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    net: fix removing a namespace with conflicting altnames

to the 6.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-fix-removing-a-namespace-with-conflicting-altnam.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 43571c969a161b4d3602a3f69d022be34180c33f
Author: Jakub Kicinski <kuba@xxxxxxxxxx>
Date:   Thu Jan 18 16:58:59 2024 -0800

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

diff --git a/net/core/dev.c b/net/core/dev.c
index e480afb50d4c..d72a4ff689ca 100644
--- 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 fa2e9c5c4122..f2037d402144 100644
--- 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);