Openwall GNU/*/Linux - a small security-enhanced Linux distro for servers
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Thu, 11 Apr 2019 10:39:20 +0200
From: Alexander Potapenko <glider@...gle.com>
To: Kees Cook <keescook@...omium.org>
Cc: Masahiro Yamada <yamada.masahiro@...ionext.com>, James Morris <jmorris@...ei.org>, 
	"Serge E. Hallyn" <serge@...lyn.com>, 
	linux-security-module <linux-security-module@...r.kernel.org>, 
	linux-kbuild <linux-kbuild@...r.kernel.org>, Nick Desaulniers <ndesaulniers@...gle.com>, 
	Kostya Serebryany <kcc@...gle.com>, Dmitry Vyukov <dvyukov@...gle.com>, Sandeep Patil <sspatil@...roid.com>, 
	Laura Abbott <labbott@...hat.com>, Kernel Hardening <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH v4 2/3] initmem: introduce CONFIG_INIT_ALL_HEAP

On Wed, Apr 10, 2019 at 6:09 PM Kees Cook <keescook@...omium.org> wrote:
>
> On Wed, Apr 10, 2019 at 6:18 AM Alexander Potapenko <glider@...gle.com> wrote:
> >
> > This config option adds the possibility to initialize newly allocated
> > pages and heap objects with a 0xAA pattern.
> > There's already a number of places where allocations are initialized
> > based on the presence of __GFP_ZERO flag. We just change this code so
> > that under CONFIG_INIT_ALL_HEAP these allocations are always initialized
> > with either 0x00 or 0xAA depending on the __GFP_ZERO.
>
> Why not just make __GFP_ZERO unconditional instead? This looks like
> it'd be simpler and not need arch-specific implementation?
Right, but it would mean we can only initialize with 0x00 pattern.
I believe that for testing purposes a nonzero pattern is better,
because it'll not only assure the execution is deterministic, but will
also uncover logic bugs earlier (see the discussion at
https://reviews.llvm.org/D54604?id=174471)
For hardening purposes the pattern shouldn't matter much.

If you think arch-specific code is too much of a trouble, we could
implement clear_page_pattern() using memset() on every architecture,
but allow the user to choose between slow (0xAA) and production (0x00)
modes.
> --
> Kees Cook



-- 
Alexander Potapenko
Software Engineer

Google Germany GmbH
Erika-Mann-Straße, 33
80636 München

Geschäftsführer: Paul Manicle, Halimah DeLaine Prado
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg

Powered by blists - more mailing lists

Your e-mail address:

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.