linux-kernel - Re: [PATCH qemu] x86: don't let decompressed kernel image clobber setup

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <0c7ea5cd-1623-ddec-91e5-9d576b079349@linaro.org>
Date:   Thu, 29 Dec 2022 08:28:35 +0100
From:   Philippe Mathieu-Daudé <philmd@...aro.org>
To:     "Jason A. Donenfeld" <Jason@...c4.com>,
        "H. Peter Anvin" <hpa@...or.com>
Cc:     pbonzini@...hat.com, ebiggers@...nel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, qemu-devel@...gnu.org,
        ardb@...nel.org, kraxel@...hat.com, bp@...en8.de
Subject: Re: [PATCH qemu] x86: don't let decompressed kernel image clobber
 setup_data

On 29/12/22 03:31, Jason A. Donenfeld wrote:
> Hi,
> 
> Read this message in a fixed width text editor with a lot of columns.
> 
> On Wed, Dec 28, 2022 at 03:58:12PM -0800, H. Peter Anvin wrote:
>> Glad you asked.
>>
>> So the kernel load addresses are parameterized in the kernel image
>> setup header. One of the things that are so parameterized are the size
>> and possible realignment of the kernel image in memory.
>>
>> I'm very confused where you are getting the 64 MB number from. There
>> should not be any such limitation.

[...]

Thanks for the diagrams. Feel free to include them in the commit
description ;)

>> In general, setup_data should be able to go anywhere the initrd can
>> go, and so is subject to the same address cap (896 MB for old kernels,
>> 4 GB on newer ones; this address too is enumerated in the header.)
> 
> It would be theoretically possible to attach it to the initrd image
> instead of to the kernel image. As a last resort, I guess I can look
> into doing that. However, that's going to require some serious rework
> and plumbing of a lot of different components. So if I can make it work
> as is, that'd be ideal. However, I need to figure out this weird 62 meg
> limitation.
> 
> Any ideas on that?

Could it be a limitation (internal buffer) of the decompressor?