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Date: Tue, 12 Feb 2019 05:08:03 +0400
From: "igor.stoppa@...il.com" <igor.stoppa@...il.com>
To: Kees Cook <keescook@...omium.org>
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 Tue, 12 Feb 2019, 4.47 Kees Cook <keescook@...omium.org wrote:
> On Mon, Feb 11, 2019 at 4:37 PM Igor Stoppa <igor.stoppa@...il.com> wrote:
> >
> >
> >
> > On 12/02/2019 02:09, Kees Cook wrote:
> > > On Mon, Feb 11, 2019 at 3:28 PM Igor Stoppa <igor.stoppa@...il.com>
> wrote:
> > > It looked like only the memset() needed architecture support. Is there
> > > a reason for not being able to implement memset() in terms of an
> > > inefficient put_user() loop instead? That would eliminate the need for
> > > per-arch support, yes?
> >
> > So far, yes, however from previous discussion about power arch, I
> > understood this implementation would not be so easy to adapt.
> > Lacking other examples where the extra mapping could be used, I did not
> > want to add code without a use case.
> >
> > Probably both arm and x86 32 bit could do, but I would like to first get
> > to the bitter end with memory protection (the other 2 thirds).
> >
> > Mostly, I hated having just one arch and I also really wanted to have
> arm64.
>
> Right, I meant, if you implemented the _memset() case with put_user()
> in this version, you could drop the arch-specific _memset() and shrink
> the patch series. Then you could also enable this across all the
> architectures in one patch. (Would you even need the Kconfig patches,
> i.e. won't this "Just Work" on everything with an MMU?)
>
I had similar thoughts, but this answer [1] deflated my hopes (if I
understood it correctly).
It seems that each arch needs to be massaged in separately.
--
igor
[1] https://www.openwall.com/lists/kernel-hardening/2018/12/12/15
>
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