linux-kernel - Re: [Security] proactive defense: using read-only memory, RO/NX modules

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Date:	Thu, 11 Nov 2010 10:07:13 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Kees Cook <kees.cook@...onical.com>
Cc:	matthieu castet <castet.matthieu@...e.fr>,
	Siarhei Liakh <sliakh.lkml@...il.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Arjan van de Ven <arjan@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [Security] proactive defense: using read-only memory, RO/NX
 modules


* Kees Cook <kees.cook@...onical.com> wrote:

> Hi Ingo,
> 
> On Wed, Nov 10, 2010 at 10:04:15AM +0100, Ingo Molnar wrote:
> > * Kees Cook <kees.cook@...onical.com> wrote:
> > > Oh, well, yes, that's a good reason. :) Where was this covered? I'd like to help 
> > > get it reproduced and ironed out.
> > 
> > Matthieu Castet seems to have dusted off those patches and submitted two of them in 
> > this mail:
> > 
> >   Subject: [RFC] reworked NX protection for kernel data
> > 
> > Matthieu, are you still interested in this topic?
> > 
> > The original, broken patches were these -tip commits:
> > 
> >  1e858c081af5: x86, mm: RO/NX protection for loadable kernel modules
> >  18c60ddc9eff: x86, mm: NX protection for kernel data
> >  c226a2feba21: x86, mm: Set first MB as RW+NX
> >  b29d530510d4: x86, mm: Correcting improper large page preservation
> > 
> > I reported one of the crashes in:
> > 
> >   Subject: Re: [tip:x86/mm] x86, mm: Set first MB as RW+NX
> > 
> > on lkml.
> 
> Thanks for looking this up!
> 
> Can we get 1e858c081af5 and 18c60ddc9eff back in, and then work forward
> from there?

Yeah. Please port them to latest -tip:

   http://people.redhat.com/mingo/tip.git/README

And give them some testing, and send out the new series. I'll re-report the crash to 
you for a new kernel, if it still occurs.

(Please also keep Rusty and Linus Cc:-ed for the module bits.)

In hindsight, i think the kernel/module.c bits should be in arch/x86/kernel/module.c 
- the new code is full of x86 only names and facilities.

Also, please remove various checkpatch col80 artifacts, such as:

+               if (end_pfn > begin_pfn)
+                       set_memory_nx(begin_pfn << PAGE_SHIFT,
+                                               end_pfn - begin_pfn);

that should be:

+               if (end_pfn > begin_pfn)
+                       set_memory_nx(begin_pfn << PAGE_SHIFT, end_pfn - begin_pfn);

Thanks,

	Ingo
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