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Message-ID: <CAGXu5jL0ZOzTo2sXiWkgemcwHusX4YuM9b_9y-MZ2THuDoRC+g@mail.gmail.com> 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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