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From: David Howells <dhowells@redhat.com>
In-Reply-To: <20180816073407.12567-1-avagin@openvz.org>
References: <20180816073407.12567-1-avagin@openvz.org>
To: Andrei Vagin <avagin@openvz.org>
Cc: dhowells@redhat.com, linux-fsdevel@vger.kernel.org,
        Andrei Vagin <avagin@gmail.com>,
        Eric Biederman <ebiederm@xmission.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH dhowells/mount-api] proc: set a proper user namespace for fs_context
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Date: Tue, 21 Aug 2018 08:33:26 +0100
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Andrei Vagin <avagin@openvz.org> wrote:

> A user namespace should be taken from a pidns for which a procfs is created.

That would seem wrong.  Shouldn't the superblock user_ns be from the mounter?

Adding Al and Eric to the list to get their opinion.

David

> Signed-off-by: Andrei Vagin <avagin@gmail.com>
> ---
>  fs/proc/root.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/fs/proc/root.c b/fs/proc/root.c
> index 1d6e5bfa30cc..1419b48a89ab 100644
> --- a/fs/proc/root.c
> +++ b/fs/proc/root.c
> @@ -315,6 +315,11 @@ int pid_ns_prepare_proc(struct pid_namespace *ns)
>  	if (IS_ERR(fc))
>  		return PTR_ERR(fc);
>  
> +	if (fc->user_ns != ns->user_ns) {
> +		put_user_ns(fc->user_ns);
> +		fc->user_ns = get_user_ns(ns->user_ns);
> +	}
> +
>  	ctx = fc->fs_private;
>  	if (ctx->pid_ns != ns) {
>  		put_pid_ns(ctx->pid_ns);