MIME-Version: 1.0
In-Reply-To: <1490887379-25880-1-git-send-email-tixxdz@gmail.com>
References: <1490887379-25880-1-git-send-email-tixxdz@gmail.com>
From: Andy Lutomirski <luto@amacapital.net>
Date: Thu, 30 Mar 2017 12:12:31 -0700
Message-ID: <CALCETrWooKTtViVh4ik9e-3nLs3NET9wptgxhjS9V499sfUJQA@mail.gmail.com>
Subject: Re: [PATCH RFC 0/4] proc: support multiple separate proc instances
 per pidnamespace
To: Djalal Harouni <tixxdz@gmail.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Andy Lutomirski <luto@kernel.org>,
        Alexey Gladkov <gladkov.alexey@gmail.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linux API <linux-api@vger.kernel.org>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Oleg Nesterov <oleg@redhat.com>, Pavel Emelyanov <xemul@parallels.com>,
        James Bottomley <James.Bottomley@hansenpartnership.com>,
        Kees Cook <keescook@chromium.org>, Dongsu Park <dpark@posteo.net>,
        Ingo Molnar <mingo@kernel.org>, Michal Hocko <mhocko@suse.com>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        "kernel-hardening@lists.openwall.com" 
        <kernel-hardening@lists.openwall.com>,
        LSM List <linux-security-module@vger.kernel.org>
Content-Type: text/plain; charset=UTF-8
Sender: linux-kernel-owner@vger.kernel.org
Content-Transfer-Encoding: 8bit
Content-Length: 2466
Lines: 69

On Thu, Mar 30, 2017 at 8:22 AM, Djalal Harouni <tixxdz@gmail.com> wrote:
> Hi,
>
> This RFC can be applied on top of Linus' tree 89970a04d7
>
> This RFC implements support for multiple separate proc instances inside
> the same pid namespace. This allows to solve lot of problems that
> today's use case face.
>
> Historically procfs was tied to pid namespaces, and mount options were
> propagated to all other procfs instances in the same pid namespace. This
> solved several use cases in that time. However today we face new
> problems, there are mutliple container implementations there, some of
> them want to hide pid entries, others want to hide non-pid entries,
> others want to have sysctlfs, others want to share pid namespace with
> private procfs mounts. All these with current implementation won't work
> since all options will be propagated to all procfs mounts.
>
> This series allow to have new instances of procfs per pid namespace where
> each instance can have its own mount option inside the same pid namespace.
> This was also suggested by Andy Lutomirski.
>
>
> Now:
> $ sudo mount -t proc -o unshare,hidepid=2 none /test
>
> The option 'unshare' will allow to mount a new instance of procfs inside
> the same pid namespace.
>
> Before:
> $ stat /proc/slabinfo
>
>   File: ‘/proc/slabinfo’
>   Size: 0               Blocks: 0          IO Block: 1024   regular empty file
> Device: 4h/4d   Inode: 4026532046  Links: 1
>
> $ stat /test3/slabinfo
>
>   File: ‘/test3/slabinfo’
>   Size: 0               Blocks: 0          IO Block: 1024   regular empty file
> Device: 4h/4d   Inode: 4026532046  Links: 1
>
>
> After:
> $ stat /proc/slabinfo
>
>   File: ‘/proc/slabinfo’
>   Size: 0               Blocks: 0          IO Block: 1024   regular empty file
> Device: 4h/4d   Inode: 4026532046  Links: 1
>
> $ stat /test3/slabinfo
>
>   File: ‘/test3/slabinfo’
>   Size: 0               Blocks: 0          IO Block: 1024   regular empty file
> Device: 31h/49d Inode: 4026532046  Links: 1
>
>
> Any better name for the option 'unshare' ? suggestions ?
>
> I was going to use 'version=2' but then this may sound more like a
> proc2 fs which currently impossible to implement since it will share
> locks with the old proc.
>
>
> Al, Eric any comments please ?

I like the concept, except that I think it would be nice to avoid
needing 'unshare', perhaps by making unsharing the default and making
hidepid work backwards compatibly if needed.