linux-kernel - Re: [PATCH 0/3] userfaultfd: allow to forbid unprivileged users

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Message-ID: <58e63635-fc1b-cb53-a4d1-237e6b8b7236@oracle.com>
Date:   Tue, 12 Mar 2019 12:59:34 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Peter Xu <peterx@...hat.com>, linux-kernel@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Hugh Dickins <hughd@...gle.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Maxime Coquelin <maxime.coquelin@...hat.com>,
        kvm@...r.kernel.org, Jerome Glisse <jglisse@...hat.com>,
        Pavel Emelyanov <xemul@...tuozzo.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Martin Cracauer <cracauer@...s.org>,
        Denis Plotnikov <dplotnikov@...tuozzo.com>, linux-mm@...ck.org,
        Marty McFadden <mcfadden8@...l.gov>,
        Maya Gokhale <gokhale2@...l.gov>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Kees Cook <keescook@...omium.org>,
        Mel Gorman <mgorman@...e.de>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        linux-fsdevel@...r.kernel.org,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 0/3] userfaultfd: allow to forbid unprivileged users

On 3/11/19 2:36 AM, Peter Xu wrote:
> 
> The "kvm" entry is a bit special here only to make sure that existing
> users like QEMU/KVM won't break by this newly introduced flag.  What
> we need to do is simply set the "unprivileged_userfaultfd" flag to
> "kvm" here to automatically grant userfaultfd permission for processes
> like QEMU/KVM without extra code to tweak these flags in the admin
> code.

Another user is Oracle DB, specifically with hugetlbfs.  For them, we would
like to add a special case like kvm described above.  The admin controls
who can have access to hugetlbfs, so I think adding code to the open
routine as in patch 2 of this series would seem to work.

However, I can imagine more special cases being added for other users.  And,
once you have more than one special case then you may want to combine them.
For example, kvm and hugetlbfs together.
-- 
Mike Kravetz