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From: Kees Cook <keescook@chromium.org>
Date: Wed, 22 Jun 2016 10:05:51 -0700
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Subject: Re: [kernel-hardening] [PATCH v7 0/9] x86/mm: memory area address KASLR
To: Thomas Garnier <thgarnie@google.com>
Cc: Jason Cooper <jason@lakedaemon.net>, "kernel-hardening@lists.openwall.com" <kernel-hardening@lists.openwall.com>, Ingo Molnar <mingo@kernel.org>, Andy Lutomirski <luto@kernel.org>, "x86@kernel.org" <x86@kernel.org>, Borislav Petkov <bp@suse.de>, Baoquan He <bhe@redhat.com>, Yinghai Lu <yinghai@kernel.org>, Juergen Gross <jgross@suse.com>, Matt Fleming <matt@codeblueprint.co.uk>, Toshi Kani <toshi.kani@hpe.com>, Andrew Morton <akpm@linux-foundation.org>, Dan Williams <dan.j.williams@intel.com>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Dave Hansen <dave.hansen@linux.intel.com>, Xiao Guangrong <guangrong.xiao@linux.intel.com>, Martin Schwidefsky <schwidefsky@de.ibm.com>, "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>, Alexander Kuleshov <kuleshovmail@gmail.com>, Alexander Popov <alpopov@ptsecurity.com>, Dave Young <dyoung@redhat.com>, Joerg Roedel <jroedel@suse.de>, Lv Zheng <lv.zheng@intel.com>, Mark Salter <msalter@redhat.com>, Dmitry Vyukov <dvyukov@google.com>, Stephen Smalley <sds@tycho.nsa.gov>, Boris Ostrovsky <boris.ostrovsky@oracle.com>, Christian Borntraeger <borntraeger@de.ibm.com>, Jan Beulich <JBeulich@suse.com>, LKML <linux-kernel@vger.kernel.org>, Jonathan Corbet <corbet@lwn.net>, "linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>
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On Wed, Jun 22, 2016 at 8:59 AM, Thomas Garnier <thgarnie@google.com> wrote:
> On Wed, Jun 22, 2016 at 5:47 AM, Jason Cooper <jason@lakedaemon.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