linux-kernel - Re: [RFC] stack and heap are executable on x86

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Message-ID: <50D49E0A.1080609@zytor.com>
Date:	Fri, 21 Dec 2012 09:36:10 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Yinghai Lu <yinghai@...nel.org>
CC:	Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	Jim Kukunas <james.t.kukunas@...ux.intel.com>,
	Arjan van de Ven <arjan@...radead.org>
Subject: Re: [RFC] stack and heap are executable on x86_64

On 12/21/2012 09:28 AM, Yinghai Lu wrote:
> 
> which line?
> 
>  0xffffffff83000000-0xffffffff83c00000          12M     RW         PSE
> GLB  x  pmd
> 
> my kernel INIT_SIZE is 27M, and it includes everything that i needed
> in the kernel.
> 

We should NEVER have RW + x at the same time (at least when the kernel
is compiled properly.)  Looks like your patch does get rid of a bunch of
stuff in the low mapping -- although the low mapping really should never
be +x at all -- but there are still problems with the high mapping.

Oh yes, and then there is EFI.  If that means we need to keep a
completely separate page tables for EFI than so be it...

	-hpa

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