kernel-hardening - Re: [PATCH v2 00/29] implement KASLR for ARM

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Message-ID: <CAKv+Gu8ngWMvkmNr77SzL8fEvSc5K-OntoZQ53vgWVLHhAajaw@mail.gmail.com>
Date: Wed, 6 Sep 2017 18:30:55 +0100
From: Ard Biesheuvel <ard.biesheuvel@...aro.org>
To: Tony Lindgren <tony@...mide.com>
Cc: "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, 
	Kernel Hardening <kernel-hardening@...ts.openwall.com>, Arnd Bergmann <arnd@...db.de>, 
	Nicolas Pitre <nico@...aro.org>, Russell King <linux@...linux.org.uk>, 
	Kees Cook <keescook@...omium.org>, Thomas Garnier <thgarnie@...gle.com>, 
	Marc Zyngier <marc.zyngier@....com>, Mark Rutland <mark.rutland@....com>, 
	Matt Fleming <matt@...eblueprint.co.uk>, Dave Martin <dave.martin@....com>
Subject: Re: [PATCH v2 00/29] implement KASLR for ARM

On 6 September 2017 at 18:12, Tony Lindgren <tony@...mide.com> wrote:
> * Ard Biesheuvel <ard.biesheuvel@...aro.org> [170906 09:36]:
>> Turns out I am calculating the top of DRAM incorrectly for boards
>> where less memory is present than the size of the lowmem region.
>>
>> Could you try this please? (Apologies for the whitespace)
>
> I think for 10 or so units per year you can actually buy
> a non-mangling outgoing SMTP service if nothing else helps..
>

Yeah, you're right, apologies. I use git-send-email mostly, but not
for inline snippets like this. And it is not actually the SMTP service
but the web client that mangles the whitespace

> Anyways, you patch manually applied fixed most of the random
> boot hangs for me, but I did see a new one after 11 boot
> attempts, see below.
>
> Regards,
>
> Tony
>
> 8< --------------
> Kernel image @ 0x81000000 [ 0x000000 - 0x426300 ]
> ## Flattened Device Tree blob at 84000000
>    Booting using the fdt blob at 0x84000000
>    Loading Device Tree to 86feb000, end 86fff2d5 ... OK
>
> Starting kernel ...
>
> regions.image_size:00e00000
> regions.pa_start:80000000
> regions.pa_end:87200000
> regions.zimage_start:81000000
> regions.zimage_size:00437320
> regions.dtb_start:86feb000
> regions.dtb_size:00012000
> regions.initrd_start:00000000
> regions.initrd_size:00000000
> num:00000028
> num:00000025
> *kaslr_offset:05e00000
> Uncompressing Linux... done, booting the kernel.
> Warning: Neither atags nor dtb found

OK, so in this case, 80000000 + 00e00000 + 05e00000 == 86c00000, which
is still below the DTB, but apparently, it has corrupted it anyway.

I will try to figure out what's going on here.

Thanks again for taking the time,
Ard.

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