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From:   Kees Cook <keescook@chromium.org>
Date:   Tue, 23 Apr 2019 15:19:15 -0700
Message-ID: <CAGXu5jJbgmq1QS-+FO7Oe9KLrAmT+ivUjSochmHBgbvHkuj+VQ@mail.gmail.com>
Subject: Re: [PATCH v2 1/1] userfaultfd/sysctl: add vm.unprivileged_userfaultfd
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     Peter Xu <peterx@redhat.com>, LKML <linux-kernel@vger.kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Hugh Dickins <hughd@google.com>,
        Luis Chamberlain <mcgrof@kernel.org>,
        Maxime Coquelin <maxime.coquelin@redhat.com>,
        Maya Gokhale <gokhale2@llnl.gov>,
        Jerome Glisse <jglisse@redhat.com>,
        Pavel Emelyanov <xemul@virtuozzo.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Martin Cracauer <cracauer@cons.org>,
        Denis Plotnikov <dplotnikov@virtuozzo.com>,
        Linux-MM <linux-mm@kvack.org>,
        Marty McFadden <mcfadden8@llnl.gov>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Mike Rapoport <rppt@linux.vnet.ibm.com>,
        Kees Cook <keescook@chromium.org>,
        Mel Gorman <mgorman@suse.de>,
        "Kirill A . Shutemov" <kirill@shutemov.name>,
        Linux API <linux-api@vger.kernel.org>,
        "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
        "Dr . David Alan Gilbert" <dgilbert@redhat.com>
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On Tue, Mar 19, 2019 at 11:02 AM Andrew Morton
<akpm@linux-foundation.org> wrote:
>
> On Tue, 19 Mar 2019 11:07:22 +0800 Peter Xu <peterx@redhat.com> wrote:
>
> > Add a global sysctl knob "vm.unprivileged_userfaultfd" to control
> > whether userfaultfd is allowed by unprivileged users.  When this is
> > set to zero, only privileged users (root user, or users with the
> > CAP_SYS_PTRACE capability) will be able to use the userfaultfd
> > syscalls.
>
> Please send along a full description of why you believe Linux needs
> this feature, for me to add to the changelog.  What is the benefit to
> our users?  How will it be used?
>
> etcetera.  As it was presented I'm seeing no justification for adding
> the patch!

Was there a v3 of this patch? I'd still really like to have this knob added. :)

Thanks!

-- 
Kees Cook