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Message-ID: <CAGXu5jLYA2tOEEk0ov6nU8d3k2pFZ8cY2jiB_pZthhzkagcz=A@mail.gmail.com>
Date: Mon, 11 Apr 2016 11:47:14 -0700
From: Kees Cook <keescook@...omium.org>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: James Morse <james.morse@....com>, Linus Torvalds <torvalds@...ux-foundation.org>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>, Matt Redfearn <matt.redfearn@...tec.com>,
Yves-Alexis Perez <corsac@...ian.org>, Emrah Demir <ed@...sec.com>, Jonathan Corbet <corbet@....net>,
"x86@...nel.org" <x86@...nel.org>, "Rafael J. Wysocki" <rjw@...ysocki.net>, Len Brown <len.brown@...el.com>,
Pavel Machek <pavel@....cz>, Borislav Petkov <bp@...e.de>, Andy Lutomirski <luto@...nel.org>,
"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>, Linux PM list <linux-pm@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH] Prefer kASLR over Hibernation
On Mon, Apr 11, 2016 at 11:21 AM, Geert Uytterhoeven
<geert@...ux-m68k.org> wrote:
> On Mon, Apr 11, 2016 at 8:03 PM, Kees Cook <keescook@...omium.org> wrote:
>> On Mon, Apr 11, 2016 at 1:00 AM, James Morse <james.morse@....com> wrote:
>>> On 06/04/16 20:44, Kees Cook wrote:
>>>> When building with both CONFIG_HIBERNATION and CONFIG_RANDOMIZE_BASE,
>>>> one or the other must be chosen at boot-time. Until now, hibernation
>>>> was selected when no choice was made on the command line.
>>>>
>>>> To make the security benefits of kASLR more widely available to end
>>>> users (since the use of hibernation is becoming more rare and kASLR,
>>>> already available on x86, will be available on arm64 and MIPS soon),
>>>> this changes the default to preferring kASLR over hibernation. Users
>>>> wanting hibernation can turn off kASLR by adding "nokaslr" to the kernel
>>>> command line.
>>>
>>> While hibernate isn't yet merged for arm64, it does work with kASLR in v4.6-rc*,
>>> it would be a shame to have to choose at boot time, (but that's my problem to
>>> fix if/when its merged).
>>
>> Ah, interesting, so they work together on arm64? (i.e. you've actually
>> tested a boot loader that provides the seed for kASLR to operate?)
>
> Probably the PS3 people can provide us with a good tool to generate a
> seed that makes hibernation work all the time ;-)
>
> https://xkcd.com/221/
:)
http://assets.amuniversal.com/321a39e06d6401301d80001dd8b71c47
-Kees
--
Kees Cook
Chrome OS & Brillo Security
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