linux-kernel - Re: [PATCH v6 04/13] arm64/kvm: hide ptrauth from guests

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Message-ID: <861s6scnr4.wl-marc.zyngier@arm.com>
Date:   Sat, 08 Dec 2018 10:32:31 +0000
From:   Marc Zyngier <marc.zyngier@....com>
To:     Kristina Martsenko <kristina.martsenko@....com>
Cc:     <linux-arm-kernel@...ts.infradead.org>,
        Adam Wallis <awallis@...eaurora.org>,
        Amit Kachhap <amit.kachhap@....com>,
        Andrew Jones <drjones@...hat.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Christoffer Dall <christoffer.dall@....com>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave P Martin <dave.martin@....com>,
        Jacob Bramley <jacob.bramley@....com>,
        Kees Cook <keescook@...omium.org>,
        Mark Rutland <mark.rutland@....com>,
        Ramana Radhakrishnan <ramana.radhakrishnan@....com>,
        Richard Henderson <richard.henderson@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Will Deacon <will.deacon@....com>,
        <kvmarm@...ts.cs.columbia.edu>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 04/13] arm64/kvm: hide ptrauth from guests

On Fri, 07 Dec 2018 18:39:22 +0000,
Kristina Martsenko <kristina.martsenko@....com> wrote:
> 
> From: Mark Rutland <mark.rutland@....com>
> 
> In subsequent patches we're going to expose ptrauth to the host kernel
> and userspace, but things are a bit trickier for guest kernels. For the
> time being, let's hide ptrauth from KVM guests.
> 
> Regardless of how well-behaved the guest kernel is, guest userspace
> could attempt to use ptrauth instructions, triggering a trap to EL2,
> resulting in noise from kvm_handle_unknown_ec(). So let's write up a
> handler for the PAC trap, which silently injects an UNDEF into the
> guest, as if the feature were really missing.
> 
> Signed-off-by: Mark Rutland <mark.rutland@....com>
> Signed-off-by: Kristina Martsenko <kristina.martsenko@....com>
> Reviewed-by: Andrew Jones <drjones@...hat.com>
> Reviewed-by: Christoffer Dall <christoffer.dall@....com>
> Cc: Marc Zyngier <marc.zyngier@....com>
> Cc: kvmarm@...ts.cs.columbia.edu

Reviewed-by: Marc Zyngier <marc.zyngier@....com>

	M.

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