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Date: Thu, 14 Apr 2016 13:14:07 -0700
From: Kees Cook <>
To: Pavel Machek <>
Cc: Linus Torvalds <>, "Rafael J. Wysocki" <>, 
	Ingo Molnar <>, James Morse <>, 
	Ard Biesheuvel <>, Matt Redfearn <>, 
	Yves-Alexis Perez <>, Emrah Demir <>, Jonathan Corbet <>, 
	"" <>, Len Brown <>, Borislav Petkov <>, 
	Andy Lutomirski <>, "" <>, 
	Linux PM list <>, LKML <>, 
	"" <>
Subject: Re: [PATCH v2] kaslr: allow kASLR to be default over Hibernation

On Thu, Apr 14, 2016 at 1:01 PM, Pavel Machek <> wrote:
> Hi!
>> Since kASLR and Hibernation can not currently coexist at runtime
>> on x86, the default behavior was to disable kASLR by default when
>> CONFIG_HIBERNATION was present (to retain original behavior).
>> The behavior of kASLR on arm64 (and soon MIPS) is to be enabled by
>> default when selected at build time. Since arm64 Hibernation does not
>> conflict with kASLR, this fixes the hibernation argument parsing to be
>> x86-specific. Additionally, since end users want to be able to select
>> kASLR on x86 by default at build time, create CONFIG_RANDOMIZE_BASE_ON
>> that is present only on x86.
>> Signed-off-by: Kees Cook <>
> I believe this is bad idea. arm64 shows that kaslr and hibernation can
> coexist, and hibernation is still useful when your battery runs out.

What? I'm confused -- this patch leaves the x86 behavior as-is by
default but allows hibernation to work with arm64. (For example, right
now, if you boot arm64 with "kaslr" kernel argument, hibernation will
get needlessly disabled.)


Kees Cook
Chrome OS & Brillo Security

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