linux-kernel - Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount

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Message-ID: <8760kbg5ga.fsf@xmission.com>
Date:   Wed, 15 Feb 2017 22:37:41 +1300
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Djalal Harouni <tixxdz@...il.com>
Cc:     James Bottomley <James.Bottomley@...senpartnership.com>,
        Josh Triplett <josh@...htriplett.org>,
        Christoph Hellwig <hch@...radead.org>,
        Amir Goldstein <amir73il@...il.com>, Chris Mason <clm@...com>,
        Theodore Tso <tytso@....edu>,
        Andy Lutomirski <luto@...nel.org>,
        Seth Forshee <seth.forshee@...onical.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        LSM List <linux-security-module@...r.kernel.org>,
        Dongsu Park <dongsu@...ocode.com>,
        David Herrmann <dh.herrmann@...glemail.com>,
        Miklos Szeredi <mszeredi@...hat.com>,
        Alban Crequy <alban.crequy@...il.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        "Serge E. Hallyn" <serge@...lyn.com>, Phil Estes <estesp@...il.com>
Subject: Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount

Djalal Harouni <tixxdz@...il.com> writes:

> On Mon, Feb 13, 2017 at 11:15 AM, Eric W. Biederman
> <ebiederm@...ssion.com> wrote:
>> James Bottomley <James.Bottomley@...senPartnership.com> writes:

>>> So is this.  Basically anything that begins by mounting gets a super
>>> block and can use the s_user_ns to map from the filesystem view to the
>>> kernel view of ids.  Apart from greater sophistication in the
>>> parametrisation, it sounds like we have all the machinery you need.
>>>  I'm sure the containers people will consider reasonable patches to
>>> change this.
>>
>> Yes.
>>
>> And to be clear we have all of that merged now and mostly present and
>> hooked up in all filesystems without any shiftfs like changes needed.
>>
>> To use this with a filesystem a last pass needs to be had to verify that
>> the cases where something does not map are handled cleanly.
>
> Still this does not answer the question how to dynamically
> *attach/share* data or read-only volumes as defined by
> orchestration/container tools into several containers. Am I missing
> something or is the plan to have per superblock mount for each one ?

Agreed.  That is a related problem and the problem that shiftfs
is working to solve.

If you only need a single mapping the infrastructure is basically done
in the kernel today.  If you need multiple mappings we need something
more.

Eric