linux-kernel - Re: [PATCH 3/7] x86, kaslr: find minimum safe relocation position

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Message-ID: <CAGXu5j+hm8whuGxJ9PBEdxrSwpdH9a-S5-7ReVmb+COyRo9=uw@mail.gmail.com>
Date:	Thu, 3 Oct 2013 15:43:11 -0700
From:	Kees Cook <keescook@...omium.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>,
	"kernel-hardening@...ts.openwall.com" 
	<kernel-hardening@...ts.openwall.com>,
	Aaron Durbin <adurbin@...gle.com>,
	Eric Northup <digitaleric@...gle.com>,
	Julien Tinnes <jln@...gle.com>, Will Drewry <wad@...gle.com>,
	Mathias Krause <minipli@...glemail.com>,
	Zhang Yanfei <zhangyanfei@...fujitsu.com>
Subject: Re: [PATCH 3/7] x86, kaslr: find minimum safe relocation position

On Thu, Oct 3, 2013 at 3:23 PM, H. Peter Anvin <hpa@...or.com> wrote:
> On 10/03/2013 01:53 PM, Kees Cook wrote:
>> Examine all the known unsafe areas and avoid them by just raising the
>> minimum relocation position to be past them.
>>
>> Signed-off-by: Kees Cook <keescook@...omium.org>
>
>> +     /* Minimum location must be above all these regions: */
>
> This is highly problematic.  The standard protocol is to hoist the
> initramfs as high as possible in memory, so this may really unacceptably
> restrict the available range.

Doesn't this depend on the boot loader's behavior?

> It would be better to treat these the same as reserved regions in the
> e820 map as far as the address space picking algorithm is concerned.

Could this be considered a future optimization, or do you feel this is
required even for this first patch series landing?

-Kees

-- 
Kees Cook
Chrome OS Security
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