From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Xu <peterx@redhat.com>
Subject: Re: [PATCH 1/3] userfaultfd/sysctl: introduce
 unprivileged_userfaultfd
Date: Tue, 12 Mar 2019 20:26:33 +0800
Message-ID: <20190312122633.GE14108@xz-x1>
References: <20190311093701.15734-1-peterx@redhat.com>
 <20190311093701.15734-2-peterx@redhat.com>
 <20190312065830.GB9497@rapoport-lnx>
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8
Cc: 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>,
        kvm@vger.kernel.org, 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@kvack.org,
        Marty McFadden <mcfadden8@llnl.gov>,
        Maya Gokhale <gokhale2@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-fsdevel@vger.kernel.org,
To: Mike Rapoport <rppt@linux.ibm.com>
Return-path: <linux-kernel-owner@vger.kernel.org>
Content-Disposition: inline
In-Reply-To: <20190312065830.GB9497@rapoport-lnx>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: kvm.vger.kernel.org

On Tue, Mar 12, 2019 at 08:58:30AM +0200, Mike Rapoport wrote:

[...]

> > +config USERFAULTFD_UNPRIVILEGED_DEFAULT
> > +        string "Default behavior for unprivileged userfault syscalls"
> > +        depends on USERFAULTFD
> > +        default "disabled"
> > +        help
> > +          Set this to "enabled" to allow userfaultfd syscalls from
> > +          unprivileged users.  Set this to "disabled" to forbid
> > +          userfaultfd syscalls from unprivileged users.  Set this to
> > +          "kvm" to forbid unpriviledged users but still allow users
> > +          who had enough permission to open /dev/kvm.
> 
> I'd phrase it a bit differently:
> 
> This option controls privilege level required to execute userfaultfd
                      ^
                      +---- add " the default"?

> system call.
> 
> Set this to "enabled" to allow userfaultfd system call from unprivileged
> users. 
> Set this to "disabled" to allow userfaultfd system call only for users who
> have ptrace capability.
> Set this to "kvm" to restrict userfaultfd system call usage to users with
                                                                      ^
                         add " who have ptrace capability, or" -------+

> permissions to open "/dev/kvm".

I think your version is better than mine, but I'd like to confirm
about above two extra changes before I squash them into the patch. :)

Thanks!

-- 
Peter Xu