Don't cargo-cult the same thing over and over.

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 net/core/net_namespace.c | 46 ++++++++++++++++++++++++++++++++--------------
 1 file changed, 32 insertions(+), 14 deletions(-)

diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 1b6f3826dd0e..dafb3d947043 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -397,10 +397,22 @@ static __net_init void preinit_net_sysctl(struct net *net)
 }
 
 /* init code that must occur even if setup_net() is not called. */
-static __net_init void preinit_net(struct net *net, struct user_namespace *user_ns)
+static __net_init int preinit_net(struct net *net, struct user_namespace *user_ns)
 {
+	const struct proc_ns_operations *ns_ops;
+	int ret;
+
+#ifdef CONFIG_NET_NS
+	ns_ops = &netns_operations;
+#else
+	ns_ops = NULL;
+#endif
+
+	ret = ns_common_init(&net->ns, ns_ops, false);
+	if (ret)
+		return ret;
+
 	refcount_set(&net->passive, 1);
-	refcount_set(&net->ns.count, 1);
 	ref_tracker_dir_init(&net->refcnt_tracker, 128, "net_refcnt");
 	ref_tracker_dir_init(&net->notrefcnt_tracker, 128, "net_notrefcnt");
 
@@ -420,6 +432,7 @@ static __net_init void preinit_net(struct net *net, struct user_namespace *user_
 	INIT_LIST_HEAD(&net->ptype_all);
 	INIT_LIST_HEAD(&net->ptype_specific);
 	preinit_net_sysctl(net);
+	return 0;
 }
 
 /*
@@ -559,7 +572,9 @@ struct net *copy_net_ns(unsigned long flags,
 		goto dec_ucounts;
 	}
 
-	preinit_net(net, user_ns);
+	rv = preinit_net(net, user_ns);
+	if (rv < 0)
+		goto dec_ucounts;
 	net->ucounts = ucounts;
 	get_user_ns(user_ns);
 
@@ -573,6 +588,7 @@ struct net *copy_net_ns(unsigned long flags,
 
 	if (rv < 0) {
 put_userns:
+		ns_free_inum(&net->ns);
 #ifdef CONFIG_KEYS
 		key_remove_domain(net->key_domain);
 #endif
@@ -812,17 +828,14 @@ static void net_ns_net_debugfs(struct net *net)
 
 static __net_init int net_ns_net_init(struct net *net)
 {
-#ifdef CONFIG_NET_NS
-	net->ns.ops = &netns_operations;
-#endif
-	net->ns.inum = PROC_NET_INIT_INO;
-	if (net != &init_net) {
-		int ret = ns_alloc_inum(&net->ns);
-		if (ret)
-			return ret;
-	}
+	int ret = 0;
+
+	if (net == &init_net)
+		net->ns.inum = PROC_NET_INIT_INO;
+	else
+		ret = proc_alloc_inum(&to_ns_common(net)->inum);
 	net_ns_net_debugfs(net);
-	return 0;
+	return ret;
 }
 
 static __net_exit void net_ns_net_exit(struct net *net)
@@ -1282,7 +1295,12 @@ void __init net_ns_init(void)
 #ifdef CONFIG_KEYS
 	init_net.key_domain = &init_net_key_domain;
 #endif
-	preinit_net(&init_net, &init_user_ns);
+	/*
+	 * This currently cannot fail as the initial network namespace
+	 * has a static inode number.
+	 */
+	if (preinit_net(&init_net, &init_user_ns))
+		panic("Could not preinitialize the initial network namespace");
 
 	down_write(&pernet_ops_rwsem);
 	if (setup_net(&init_net))

-- 
2.47.3

On Wed, Sep 10, 2025 at 04:36:59PM +0200, Christian Brauner wrote:
>@@ -573,6 +588,7 @@ struct net *copy_net_ns(unsigned long flags,
>
> 	if (rv < 0) {
> put_userns:
>+		ns_free_inum(&net->ns);

I've ended up looking at this patch because of Jan's earlier comment about a
different issue in this patch.

Aren't we double-freeing net->ns here if setup_net() failed?

setup_net() can call ops_undo_list() on failure, which will
ns_free_inum(&net->ns) once, and then we do it again in the put_userns error
handling label.

-- 
Thanks,
Sasha

On Wed 10-09-25 16:36:59, Christian Brauner wrote:
> Don't cargo-cult the same thing over and over.
> 
> Signed-off-by: Christian Brauner <brauner@kernel.org>

One comment below.

> @@ -812,17 +828,14 @@ static void net_ns_net_debugfs(struct net *net)
>  
>  static __net_init int net_ns_net_init(struct net *net)
>  {
> -#ifdef CONFIG_NET_NS
> -	net->ns.ops = &netns_operations;
> -#endif
> -	net->ns.inum = PROC_NET_INIT_INO;
> -	if (net != &init_net) {
> -		int ret = ns_alloc_inum(&net->ns);
> -		if (ret)
> -			return ret;
> -	}
> +	int ret = 0;
> +
> +	if (net == &init_net)
> +		net->ns.inum = PROC_NET_INIT_INO;
> +	else
> +		ret = proc_alloc_inum(&to_ns_common(net)->inum);
>  	net_ns_net_debugfs(net);

Here you're calling net_ns_net_debugfs() even if proc_alloc_inum() failed
which looks like a bug to me...

								Honza

> -	return 0;
> +	return ret;
>  }
>  
>  static __net_exit void net_ns_net_exit(struct net *net)
> @@ -1282,7 +1295,12 @@ void __init net_ns_init(void)
>  #ifdef CONFIG_KEYS
>  	init_net.key_domain = &init_net_key_domain;
>  #endif
> -	preinit_net(&init_net, &init_user_ns);
> +	/*
> +	 * This currently cannot fail as the initial network namespace
> +	 * has a static inode number.
> +	 */
> +	if (preinit_net(&init_net, &init_user_ns))
> +		panic("Could not preinitialize the initial network namespace");
>  
>  	down_write(&pernet_ops_rwsem);
>  	if (setup_net(&init_net))
> 
> -- 
> 2.47.3
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR