linux-kernel - Re: [PATCH V5] x86: NX protection for kernel data

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Date:	Tue, 13 Oct 2009 07:29:07 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Siarhei Liakh <sliakh.lkml@...il.com>,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	James Morris <jmorris@...ei.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <ak@....de>, Rusty Russell <rusty@...tcorp.com.au>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	David Howells <dhowells@...hat.com>,
	Aristeu Rozanski <aris@...hat.com>
Subject: Re: [PATCH V5] x86: NX protection for kernel data

On Tue, 13 Oct 2009 16:15:27 +0200
Ingo Molnar <mingo@...e.hu> wrote:

> 
> * Arjan van de Ven <arjan@...radead.org> wrote:
> 
> > On Tue, 13 Oct 2009 07:35:28 -0400
> > Siarhei Liakh <sliakh.lkml@...il.com> wrote:
> > 
> > > ---[ Kernel Mapping ]---
> > >  0xc0000000-0xc0100000           1M     RW             GLB x  pte
> > > -0xc0100000-0xc048d000        3636K     ro             GLB x  pte
> > > -0xc048d000-0xc04d0000         268K     RW             GLB x  pte
> > > -0xc04d0000-0xc04d2000           8K     RW             GLB NX pte
> > > -0xc04d2000-0xc04d3000           4K     RW             GLB x  pte
> > > -0xc04d3000-0xc0531000         376K     RW             GLB NX pte
> > > -0xc0531000-0xc0600000         828K     RW             GLB x  pte
> > > +0xc0100000-0xc0381000        2564K     ro             GLB x  pte
> > > +0xc0381000-0xc048d000        1072K     ro             GLB NX pte
> > > +0xc048d000-0xc0600000        1484K     RW             GLB NX pte
> > >  0xc0600000-0xf7800000         882M     RW         PSE GLB NX pmd
> > >  0xf7800000-0xf79fe000        2040K     RW             GLB NX pte
> > >  0xf79fe000-0xf7a00000           8K                           pte
> > > ===============================================
> > > 
> > 
> > looks great to me; the result is 
> > * kernel is ro + x
> > * rodata is ro + NX
> > * data is RW + NX
> >
> > (and there is no "RW + x", other than the first megabyte... hmm.
> > maybe we need to look at that as well at some point)
> 
> Could we cover the first megabyte too please via a (default-disabled) 
> option? Modern Xorg shouldnt mind about that anymore, right?


I'd be surprised if anything ever did; this is the *kernel* mapping of
the first megabyte, not some userspace mapping....



-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
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