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Message-ID: <CAGXu5jK_42d+jkPr4Ck0iL52-ignY9gq-eUZ73_YuhKJERrRxA@mail.gmail.com>
Date: Wed, 22 Jun 2016 10:05:51 -0700
From: Kees Cook <keescook@...omium.org>
To: Thomas Garnier <thgarnie@...gle.com>
Cc: Jason Cooper <jason@...edaemon.net>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, Ingo Molnar <mingo@...nel.org>,
Andy Lutomirski <luto@...nel.org>, "x86@...nel.org" <x86@...nel.org>, Borislav Petkov <bp@...e.de>,
Baoquan He <bhe@...hat.com>, Yinghai Lu <yinghai@...nel.org>, Juergen Gross <jgross@...e.com>,
Matt Fleming <matt@...eblueprint.co.uk>, Toshi Kani <toshi.kani@....com>,
Andrew Morton <akpm@...ux-foundation.org>, Dan Williams <dan.j.williams@...el.com>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Dave Hansen <dave.hansen@...ux.intel.com>,
Xiao Guangrong <guangrong.xiao@...ux.intel.com>,
Martin Schwidefsky <schwidefsky@...ibm.com>,
"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
Alexander Kuleshov <kuleshovmail@...il.com>, Alexander Popov <alpopov@...ecurity.com>,
Dave Young <dyoung@...hat.com>, Joerg Roedel <jroedel@...e.de>, Lv Zheng <lv.zheng@...el.com>,
Mark Salter <msalter@...hat.com>, Dmitry Vyukov <dvyukov@...gle.com>,
Stephen Smalley <sds@...ho.nsa.gov>, Boris Ostrovsky <boris.ostrovsky@...cle.com>,
Christian Borntraeger <borntraeger@...ibm.com>, Jan Beulich <JBeulich@...e.com>,
LKML <linux-kernel@...r.kernel.org>, Jonathan Corbet <corbet@....net>,
"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH v7 0/9] x86/mm: memory area address KASLR
On Wed, Jun 22, 2016 at 8:59 AM, Thomas Garnier <thgarnie@...gle.com> wrote:
> On Wed, Jun 22, 2016 at 5:47 AM, Jason Cooper <jason@...edaemon.net> wrote:
>> Hey Kees,
>>
>> On Tue, Jun 21, 2016 at 05:46:57PM -0700, Kees Cook wrote:
>>> Notable problems that needed solving:
>> ...
>>> - Reasonable entropy is needed early at boot before get_random_bytes()
>>> is available.
>>
>> This series is targetting x86, which typically has RDRAND/RDSEED
>> instructions. Are you referring to other arches? Older x86? Also,
>> isn't this the same requirement for base address KASLR?
>>
>> Don't get me wrong, I want more diverse entropy sources available
>> earlier in the boot process as well. :-) I'm just wondering what's
>> different about this series vs base address KASLR wrt early entropy
>> sources.
>>
>
> I think Kees was referring to the refactor I did to get the similar
> entropy generation than KASLR module randomization. Our approach was
> to provide best entropy possible even if you have an older processor
> or under virtualization without support for these instructions.
> Unfortunately common on companies with a large number of older
> machines.
Right, the memory offset KASLR uses the same routines as the kernel
base KASLR. The issue is with older x86 systems, which continue to be
very common.
-Kees
--
Kees Cook
Chrome OS & Brillo Security
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