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Message-ID: <CAGXu5j+kY741QCQsdFE5=B3KuagwhBdHO0FTQPFe3cT48caWVA@mail.gmail.com>
Date: Thu, 30 Mar 2017 12:49:10 -0700
From: Kees Cook <keescook@...omium.org>
To: Russell King - ARM Linux <linux@...linux.org.uk>
Cc: Hoeun Ryu <hoeun.ryu@...il.com>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, Andy Lutomirski <luto@...nel.org>,
PaX Team <pageexec@...email.hu>, Emese Revfy <re.emese@...il.com>,
"x86@...nel.org" <x86@...nel.org>, Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>, Ard Biesheuvel <ard.biesheuvel@...aro.org>,
Christoffer Dall <christoffer.dall@...aro.org>, Mark Rutland <mark.rutland@....com>,
Suzuki K Poulose <suzuki.poulose@....com>, Laura Abbott <labbott@...hat.com>,
Hugh Dickins <hughd@...gle.com>, Steve Capper <steve.capper@....com>,
Ganapatrao Kulkarni <gkulkarni@...iumnetworks.com>, James Morse <james.morse@....com>,
Kefeng Wang <wangkefeng.wang@...wei.com>,
"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFCv2] arm64: support HAVE_ARCH_RARE_WRITE and HAVE_ARCH_RARE_WRITE_MEMCPY
On Thu, Mar 30, 2017 at 12:45 PM, Russell King - ARM Linux
<linux@...linux.org.uk> wrote:
> On Thu, Mar 30, 2017 at 12:38:15PM -0700, Kees Cook wrote:
>> Great work! I think this will need some further changes, though, since
>> it doesn't look to me like this would pass LKDTM's tests if it was
>> built as a module. (This is missing from my ARM attempt too... I
>> haven't figured out how to set the domain on the kernel modules...)
>
> You're not going to be able to do it very easily. The only way I can
> think of achieving it would be to split the module area into one
> chunk for text, one chunk for write-rare and one chunk for data.
Well, my intention was to just make the entire module area
DOMAIN_WR_RARE. It's overly permissive in the sense that non-data
changes could be made, but this is already an improvement over either
not having this feature at all or x86's version which makes all of RAM
writable.
-Kees
--
Kees Cook
Pixel Security
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