linux-kernel - Re: [PATCH] Prefer kASLR over Hibernation

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Message-ID: <CAMuHMdWVGaetgcc4yxNjodkUNPaDxq2Q2JMLr_AUkb0f65YB5w@mail.gmail.com>
Date:	Mon, 11 Apr 2016 20:21:54 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Kees Cook <keescook@...omium.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 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/

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds