linux-kernel - Re: [PATCH] ARM: mm: fix location of

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Message-ID: <20160613212515.GA1041@n2100.armlinux.org.uk>
Date:	Mon, 13 Jun 2016 22:25:16 +0100
From:	Russell King - ARM Linux <linux@...linux.org.uk>
To:	Kees Cook <keescook@...omium.org>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	Nicolas Pitre <nico@...aro.org>,
	Chris Brandt <chris.brandt@...esas.com>,
	Arnd Bergmann <arnd@...db.de>,
	Alexander Potapenko <glider@...gle.com>,
	Marc Zyngier <marc.zyngier@....com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARM: mm: fix location of _etext

On Mon, Jun 13, 2016 at 01:23:29PM -0700, Kees Cook wrote:
> On Wed, Jun 8, 2016 at 4:11 PM, Kees Cook <keescook@...omium.org> wrote:
> > The _etext position is defined to be the end of the kernel text code,
> > and should not include any part of the data segments. This interferes
> > with things that might check memory ranges and expect executable code
> > up to _etext.
> >
> > Signed-off-by: Kees Cook <keescook@...omium.org>
> 
> Can someone give this an Ack? I'd like to land it as it is a
> prerequisite to some usercopy hardening work I'm doing.

We use _etext to place the end of the "kernel code" resource in
/proc/iomem, and init_mm.end_code.  I don't think anything makes
use of init_mm.end_code, but I'm more worried about the resource.

Currently, because of where _etext is placed, "kernel code" covers
the read-only data and other read-only sections as well - I don't
know whether we need to preserve that, but this change has a side
effect of changing that.

Maybe we also need a "kernel rodata" resource?

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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