linux-kernel - Re: [PATCH v1] security: Add a new hook: inode_touch

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Message-ID: <b91513c1-ce13-f365-3d12-7ee1d4c46d48@schaufler-ca.com>
Date:   Wed, 21 Dec 2016 16:30:42 -0800
From:   Casey Schaufler <casey@...aufler-ca.com>
To:     Mickaël Salaün <mic@...ikod.net>,
        linux-kernel@...r.kernel.org
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Andreas Gruenbacher <agruenba@...hat.com>,
        Andy Lutomirski <luto@...capital.net>,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        Eric Paris <eparis@...isplace.org>,
        James Morris <james.l.morris@...cle.com>,
        John Johansen <john.johansen@...onical.com>,
        Kees Cook <keescook@...omium.org>,
        Kentaro Takeda <takedakn@...data.co.jp>,
        Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        Paul Moore <paul@...l-moore.com>,
        "Serge E . Hallyn" <serge@...lyn.com>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Vivek Goyal <vgoyal@...hat.com>, linux-fsdevel@...r.kernel.org,
        linux-security-module@...r.kernel.org
Subject: Re: [PATCH v1] security: Add a new hook: inode_touch_atime

On 12/21/2016 4:01 PM, Mickaël Salaün wrote:
> On 22/12/2016 00:33, Casey Schaufler wrote:
>> On 12/21/2016 3:15 PM, Mickaël Salaün wrote:
>>> Add a new LSM hook named inode_touch_atime which is needed to deny
>>> indirect update of extended file attributes (i.e. access time) which are
>>> not catched by the inode_setattr hook. By creating a new hook instead of
>>> calling inode_setattr, we avoid to simulate a useless struct iattr.
>>>
>>> This hook allows to create read-only environments as with read-only
>>> mount points. It can also take care of anonymous inodes.
>> What security module would use this?
> SELinux should be interested. This is useful to create sandboxes so
> other LSM may be interested too

You'll have to provide more information than that. I don't
see how this hook would help there.

> I'm working on a new LSM and I would like this kind of hook to create a
> real read-only environment.

I'm curious about how this hook would be used to do that. And about
your module. You probably want to propose the hook(s) you want to add
at the same time you propose your module. I am looking forward to
reviewing it.

> Regards,
>  Mickaël