linux-kernel - Re: [PATCH v2 09/10] netns: Add a limit on the number of net namespaces

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Date:	Mon, 25 Jul 2016 18:13:29 -0500
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Linux Containers <containers@...ts.linux-foundation.org>,
	Andy Lutomirski <luto@...capital.net>,
	Jann Horn <jann@...jh.net>, Kees Cook <keescook@...omium.org>,
	Nikolay Borisov <kernel@...p.com>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	Seth Forshee <seth.forshee@...onical.com>,
	linux-fsdevel@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-api@...r.kernel.org
Subject: Re: [PATCH v2 09/10] netns: Add a limit on the number of net
 namespaces

Quoting Eric W. Biederman (ebiederm@...ssion.com):
> Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>

Acked-by: Serge Hallyn <serge@...lyn.com>

> ---
>  include/linux/user_namespace.h |  1 +
>  kernel/user_namespace.c        |  1 +
>  net/core/net_namespace.c       | 15 +++++++++++++++
>  3 files changed, 17 insertions(+)
> 
> diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
> index 1a3a9cb93277..f86afa536baf 100644
> --- a/include/linux/user_namespace.h
> +++ b/include/linux/user_namespace.h
> @@ -27,6 +27,7 @@ enum ucounts {
>  	UCOUNT_PID_NAMESPACES,
>  	UCOUNT_UTS_NAMESPACES,
>  	UCOUNT_IPC_NAMESPACES,
> +	UCOUNT_NET_NAMESPACES,
>  	UCOUNT_CGROUP_NAMESPACES,
>  	UCOUNT_COUNTS,
>  };
> diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
> index 1cf074cb47e2..e326ca722ae0 100644
> --- a/kernel/user_namespace.c
> +++ b/kernel/user_namespace.c
> @@ -80,6 +80,7 @@ static struct ctl_table userns_table[] = {
>  	UCOUNT_ENTRY("max_pid_namespaces"),
>  	UCOUNT_ENTRY("max_uts_namespaces"),
>  	UCOUNT_ENTRY("max_ipc_namespaces"),
> +	UCOUNT_ENTRY("max_net_namespaces"),
>  	UCOUNT_ENTRY("max_cgroup_namespaces"),
>  	{ }
>  };
> diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
> index 2c2eb1b629b1..a489f192d619 100644
> --- a/net/core/net_namespace.c
> +++ b/net/core/net_namespace.c
> @@ -266,6 +266,16 @@ struct net *get_net_ns_by_id(struct net *net, int id)
>  	return peer;
>  }
>  
> +static bool inc_net_namespaces(struct user_namespace *ns)
> +{
> +	return inc_ucount(ns, UCOUNT_NET_NAMESPACES);
> +}
> +
> +static void dec_net_namespaces(struct user_namespace *ns)
> +{
> +	dec_ucount(ns, UCOUNT_NET_NAMESPACES);
> +}
> +
>  /*
>   * setup_net runs the initializers for the network namespace object.
>   */
> @@ -276,6 +286,9 @@ static __net_init int setup_net(struct net *net, struct user_namespace *user_ns)
>  	int error = 0;
>  	LIST_HEAD(net_exit_list);
>  
> +	if (!inc_net_namespaces(user_ns))
> +		return -ENFILE;
> +
>  	atomic_set(&net->count, 1);
>  	atomic_set(&net->passive, 1);
>  	net->dev_base_seq = 1;
> @@ -372,6 +385,7 @@ struct net *copy_net_ns(unsigned long flags,
>  	}
>  	mutex_unlock(&net_mutex);
>  	if (rv < 0) {
> +		dec_net_namespaces(user_ns);
>  		put_user_ns(user_ns);
>  		net_drop_ns(net);
>  		return ERR_PTR(rv);
> @@ -444,6 +458,7 @@ static void cleanup_net(struct work_struct *work)
>  	/* Finally it is safe to free my network namespace structure */
>  	list_for_each_entry_safe(net, tmp, &net_exit_list, exit_list) {
>  		list_del_init(&net->exit_list);
> +		dec_net_namespaces(net->user_ns);
>  		put_user_ns(net->user_ns);
>  		net_drop_ns(net);
>  	}
> -- 
> 2.8.3