linux-kernel - Re: [RFC PATCH v4 00/12] hardening: statically allocated protected memory

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Message-ID: <CAGXu5jJyWb7aTJpDfBPD3GqMmNaJVT0pajdrPV93xnLoOa=0Vw@mail.gmail.com>
Date:   Tue, 12 Feb 2019 14:39:02 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Igor Stoppa <igor.stoppa@...il.com>
Cc:     Igor Stoppa <igor.stoppa@...wei.com>,
        Ahmed Soliman <ahmedsoliman@...a.vt.edu>,
        linux-integrity <linux-integrity@...r.kernel.org>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        Linux-MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v4 00/12] hardening: statically allocated protected memory

On Mon, Feb 11, 2019 at 11:09 PM Igor Stoppa <igor.stoppa@...il.com> wrote:
> wr_assign() does just that.
>
> However, reading again your previous mails, I realize that I might have
> misinterpreted what you were suggesting.
>
> If the advice is to have also a default memset_user() which relies on
> put_user(), but do not activate the feature by default for every
> architecture, I definitely agree that it would be good to have it.
> I just didn't think about it before.

Yeah, I just mean you could have an arch-agnostic memset_user() implementation.

> But I now realize that most likely you were just suggesting to have
> full, albeit inefficient default support and then let various archs
> review/enhance it. I can certainly do this.

Right.

> Regarding testing I have a question: how much can/should I lean on qemu?
> In most cases the MMU might not need to be fully emulated, so I wonder
> how well qemu-based testing can ensure that real life scenarios will work.

I think qemu lets you know if it works (kvm is using the real MMU),
and baremetal will give you more stable performance numbers.

-- 
Kees Cook