linux-kernel - Re: [PATCH] KERNEL: resource: Fix bug on leakage in /proc/iomem file

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Message-ID: <CAGXu5jL33J37n4WmC5Kq1-ja1DbTOOmk1D7j4dJ7DRq1keRKNA@mail.gmail.com>
Date:	Wed, 6 Apr 2016 11:53:59 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Christian Kujau <lists@...dbynature.de>
Cc:	Emrah Demir <ed@...sec.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Dan Rosenberg <dan.j.rosenberg@...il.com>,
	Dave Jones <davej@...hat.com>,
	Kernel Hardening <kernel-hardening@...ts.openwall.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] KERNEL: resource: Fix bug on leakage in /proc/iomem file

On Wed, Apr 6, 2016 at 11:52 AM, Christian Kujau <lists@...dbynature.de> wrote:
> On Wed, 6 Apr 2016, ed@...sec.com wrote:
>> First, I wrote your attached patch, but then I thought zeroing other
>> /proc/iomem values would be better. So I changed it.
>
> On my systems, /proc/iomem, /proc/ioports and others get their
> world-readable bits removed during bootup - I guess that would mitigate
> this issue too?

Yeah, I think that'd be sufficient (that's the first patch I
suggested). It's not a strong as kptr_restrict since kptr_restrict has
mode "2", but ... I think that's some diminishing returns...

-Kees

-- 
Kees Cook
Chrome OS & Brillo Security