linux-kernel - Re: [PATCH 1/4] [tip:x86/mm] Correcting improper large page preservation

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Date:	Thu, 6 May 2010 08:19:30 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Siarhei Liakh <sliakh.lkml@...il.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-security-module@...r.kernel.org" 
	<linux-security-module@...r.kernel.org>,
	"linux-next@...r.kernel.org" <linux-next@...r.kernel.org>,
	Arjan van de Ven <arjan@...radead.org>,
	James Morris <jmorris@...ei.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <ak@....de>, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Dave Jones <davej@...hat.com>,
	Suresh Siddha <suresh.b.siddha@...el.com>
Subject: Re: [PATCH 1/4] [tip:x86/mm] Correcting improper large page
 preservation


* Siarhei Liakh <sliakh.lkml@...il.com> wrote:

> On Tue, Apr 6, 2010 at 10:51 AM, Siarhei Liakh <sliakh.lkml@...il.com> wrote:
> > On Sat, Apr 3, 2010 at 2:43 AM, Suresh Siddha <suresh.b.siddha@...el.com> wrote:
> >> On Wed, 2010-03-31 at 18:59 -0700, Siarhei Liakh wrote:
> >>> + ? ? /*
> >>> + ? ? ?* .data and .bss should always be writable.
> >>> + ? ? ?*/
> >>> + ? ? if ((within(pfn, __pa((unsigned long)_sdata) >> PAGE_SHIFT,
> >>> + ? ? ? ? ? ? ? ?__pa((unsigned long)_edata) >> PAGE_SHIFT)) ||
> >>> + ? ? ? ? (within(pfn, __pa((unsigned long)__bss_start) >> PAGE_SHIFT,
> >>> + ? ? ? ? ? ? ? ?__pa((unsigned long)__bss_stop) >> PAGE_SHIFT))) {
> >>> + ? ? ? ? ? ? pgprot_val(required) |= _PAGE_RW;
> >>> + ? ? }
> >>
> >> I have reviewed this patch and the only comment I have is:
> >>
> >> On 64bit kernels, kernel text/data mapping and kernel identity mappings
> >> are different virtual addresses mapping to same pfn ranges. For the
> >> data/bss pages, does it help (in identifying certain data corruptions
> >> more easily) in making the kernel identity mapping to be set to
> >> read-only and enforce the need of RW only for the kernel data mappings.
> >>
> >> Or is there some obscure code that uses something like
> >> __va(__pa(data_symbol)) and writes to it?
> >>
> >> If not, we can remove the __pa() constructs above and use the addr for
> >> comparisons.
> >
> > Done.
> > Patch V2 have been posted.
> 
> Does anyone have any feedback on the whole kernel RO/NX patch set? Or should 
> I re-post all 4 patches one more time?
> 
> Thank you.

Please do - i havent seen any other review feedback.

Thanks,

	Ingo
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