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Date:   Tue, 12 Mar 2019 15:53:17 +0200
From:   Mike Rapoport <rppt@linux.ibm.com>
To:     Peter Xu <peterx@redhat.com>
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,
        "Dr . David Alan Gilbert" <dgilbert@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 1/3] userfaultfd/sysctl: introduce
 unprivileged_userfaultfd
References: <20190311093701.15734-1-peterx@redhat.com>
 <20190311093701.15734-2-peterx@redhat.com>
 <20190312065830.GB9497@rapoport-lnx>
 <20190312122633.GE14108@xz-x1>
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On Tue, Mar 12, 2019 at 08:26:33PM +0800, Peter Xu wrote:
> 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. :)

I like your changes.
 
> Thanks!
> 
> -- 
> Peter Xu
> 

-- 
Sincerely yours,
Mike.