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

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Message-ID: <fd9b0950f40aaffbdaa30e9cf75a9e5b@abdsec.com>
Date:	Fri, 15 Apr 2016 12:25:19 -0400
From:	Emrah Demir <ed@...sec.com>
To:	Kees Cook <keescook@...omium.org>
Cc:	Pavel Machek <pavel@...x.de>,
	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 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.


-Emrah