linux-kernel - Re: [x86, kaslr] BUG: kernel boot hang

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Message-ID: <52D5CC2A.7030906@linux.intel.com>
Date:	Tue, 14 Jan 2014 15:45:46 -0800
From:	"H. Peter Anvin" <hpa@...ux.intel.com>
To:	Kees Cook <keescook@...omium.org>
CC:	Fengguang Wu <fengguang.wu@...el.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [x86, kaslr] BUG: kernel boot hang

On 01/14/2014 03:31 PM, Kees Cook wrote:
> On Tue, Jan 14, 2014 at 3:23 PM, H. Peter Anvin <hpa@...ux.intel.com> wrote:
>> On 01/14/2014 02:33 PM, Kees Cook wrote:
>>>
>>> Can you tell me how the initrd for quantal-core-x86_64.cgz was built
>>> in the qemu instances you're using? It seems like all the failures
>>> point to a problem with how kASLR is interacting with the initrd.
>>>
>>
>> If kASLR somehow causes the kernel to collide with the initrd that would
>> be problem...
> 
> Agreed, but I can't reproduce this yet. The initrd is on the list of
> areas that get avoided, so the fundamental design isn't broken, but
> clearly something is busted.
> 
> How long has tip:x86/kaslr been sitting in linux-next? If this is some
> interaction between kaslr and something else, perhaps merge order just
> happens to be pointing at kaslr?
> 
> Regardless, all my tests so far against next-20140114 and an initramfs
> haven't seen corruption (using the given .config). I don't have the
> same initrd, though, so I'm hoping getting that will trigger the
> glitch.
> 

Given our craptastic ELF parser I'm wondering if we at some point
overrun the kernel "safe memory zone" during decompression/parsing...

	-hpa


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