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Date: Thu, 21 Feb 2019 16:16:12 -0800
From: Kees Cook <keescook@...omium.org>
To: Russell Currey <ruscur@...sell.cc>
Cc: PowerPC <linuxppc-dev@...ts.ozlabs.org>, Michael Ellerman <mpe@...erman.id.au>,
Nick Piggin <npiggin@...il.com>, Christophe Leroy <christophe.leroy@....fr>,
Kernel Hardening <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH 0/7] Kernel Userspace Protection for radix
On Thu, Feb 21, 2019 at 4:09 PM Russell Currey <ruscur@...sell.cc> wrote:
> On Thu, 2019-02-21 at 08:07 -0800, Kees Cook wrote:
> > On Thu, Feb 21, 2019 at 1:36 AM Russell Currey <ruscur@...sell.cc>
> > wrote:
> > > The first three patches of these series are from Christophe's work
> > > and are
> > > the bare minimum framework needed to implement the support for
> > > radix.
> > >
> > > In patch 3, I have removed from Christophe's patch my
> > > implementation of
> > > the 64-bit exception handling code, since we don't have an answer
> > > for
> > > making nested exceptions work yet. This is mentioned in the final
> > > KUAP
> > > patch. Regardless, this is still a significant security
> > > improvement
> > > and greatly narrows the attack surface.
> >
> > Nice! Am I understanding correctly that with this series powerpc9 and
> > later, using radix, will pass the lkdtm tests for KUAP and KUEP (i.e.
> > EXEC_USERSPACE and ACCESS_USERSPACE)?
>
> Yes! We've had execution prevention for a while on radix (which is
> default on POWER9) since 3b10d0095a1e, the only functional thing this
> series does is allow disabling it with nosmep. This series adds access
> prevention.
Ah-ha; excellent. And CONFIG_PPC_RADIX_MMU is "default y" already. :)
--
Kees Cook
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