linux-kernel - Re: [PATCH v2] kaslr: allow kASLR to be default over Hibernation

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Message-ID: <20160416195809.GA25795@amd>
Date:	Sat, 16 Apr 2016 21:58:09 +0200
From:	Pavel Machek <pavel@...x.de>
To:	Emrah Demir <ed@...sec.com>
Cc:	Kees Cook <keescook@...omium.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Ingo Molnar <mingo@...nel.org>,
	James Morse <james.morse@....com>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	Matt Redfearn <matt.redfearn@...tec.com>,
	Yves-Alexis Perez <corsac@...ian.org>,
	Jonathan Corbet <corbet@....net>, x86@...nel.org,
	Len Brown <len.brown@...el.com>, Borislav Petkov <bp@...e.de>,
	Andy Lutomirski <luto@...nel.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, keescook@...gle.com
Subject: Re: [PATCH v2] kaslr: allow kASLR to be default over Hibernation

On Fri 2016-04-15 12:25:19, Emrah Demir wrote:
> On 2016-04-14 18:42, Kees Cook wrote:
> >On Thu, Apr 14, 2016 at 1:34 PM, Pavel Machek <pavel@...x.de> wrote:
> >>On Thu 2016-04-14 13:14:07, Kees Cook wrote:
> >>>On Thu, Apr 14, 2016 at 1:01 PM, Pavel Machek <pavel@...x.de> 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.
> 
> >>>>
> >>>> 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.)
> >>
> 
> So what about making new kernel parameters. "hibernate" and "nohibernate"
> 
> This way before decompression it will look at the parameters and depend on
> parameters it will act differently
> 
> "kaslr" "nohibernate"  -->  kASLR will enable, no hibernate
> 
> "nokaslr" "nohibernate" --> Neither of them will work
> 
> "kaslr" "hiberante"   ---> Owner has to face consequences(ARM has
> advantages)
> 
> "nokaslr" "hibernate"  ---> kASLR disabled and hibernate will works.
> 
> Before writing something I want to know your ideas.

Patch fixing hibernation with kaslr on x86 and x86-64 would be
welcome.

Adding command line options that will become useless when kernel is
fixed ... not so much.

Best regards,
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html