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

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Date:   Wed, 21 Dec 2016 22:25:57 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     Mickaël Salaün <mic@...ikod.net>
Cc:     linux-kernel@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andreas Gruenbacher <agruenba@...hat.com>,
        Andy Lutomirski <luto@...capital.net>,
        Casey Schaufler <casey@...aufler-ca.com>,
        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 Thu, Dec 22, 2016 at 12:15:06AM +0100, 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.

And LSM has absolutely no business doing that - that's what the mount
code is for.