linux-kernel - RE: [PATCH] x86: Remove a.out support

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: <5161ace381a74a63b58b0a2a2a2cb57d@AcuMS.aculab.com>
Date:   Thu, 17 Mar 2022 02:32:29 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Kees Cook' <keescook@...omium.org>,
        James Jones <linux@...innocuous.com>,
        Arnd Bergmann <arnd@...db.de>
CC:     Borislav Petkov <bp@...en8.de>,
        the arch/x86 maintainers <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] x86: Remove a.out support

From: Kees Cook
> Sent: 16 March 2022 22:30
> 
> On Wed, Mar 16, 2022 at 01:38:31PM +0100, Arnd Bergmann wrote:
> > is in the end, but it's likely easier than a standalone a.out loader
> > in user space, or a conversion to ELF format.
> 
> Yeah, the exec format is really simple. The only tricky bit was preparing
> the stack and making sure everything landed in the right place for text
> and data. James, can you try this? aln and mac run for me, but I'm not
> actually exercising them beyond dumping argument lists, etc:

Doesn't that restrict the a.out program to the address space below
the normal base address for elf programs?
So you'll only be able to load small programs - which might be ok here.

OTOH it might be possible to link the 'loader program' to a high
address - the elf loader will probably just load it.
Best to link it static to avoid shared lib mmaps
and probably try to avoid libc calls.

I was wondering what happens when malloc() starts using
sbrk() - but I guess it sees the top of the bss for the
loaded and it all works fine.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)