linux-kernel - Re: [PATCH] NX protection for kernel data : fix 32 bits S3 suspend

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Message-ID: <20110226035805.GA1656@ucw.cz>
Date:	Sat, 26 Feb 2011 04:58:06 +0100
From:	Pavel Machek <pavel@....cz>
To:	matthieu castet <castet.matthieu@...e.fr>
Cc:	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	linux-security-module@...r.kernel.org,
	Matthias Hopf <mhopf@...e.de>, rjw@...k.pl,
	Andrew Morton <akpm@...ux-foundation.org>,
	Suresh Siddha <suresh.b.siddha@...el.com>
Subject: Re: [PATCH] NX protection for kernel data : fix 32 bits S3 suspend

On Sat 2011-02-12 17:10:14, matthieu castet wrote:
> H. Peter Anvin a écrit :
> >On 02/07/2011 11:59 AM, castet.matthieu@...e.fr wrote:
> >>For .39 I hope we could remove most of the RWX rights after init (This means
> >>make low memory trampoline NX or !RW).
> >>This should be possible on :
> >>- 32 bit if wakeup use trampoline_32 [1] that doesn't enable paging in low
> >>memory (can be NX)
> >>- trampoline_64 need fix to support NX on data section. It tries to read data
> >>section before enabling NX. A possible fix is to use its own page table [2]. And
> >>the kernel one can be NX.
> >
> >No, you're really barking down the wrong path on this.  The trampoline
> >code is tiny; I don't think it is really worth trying to NX-ify it.  The
> Even if the trampoline is tiny, a hole is a hole.

What kind of hole are you talking about?

If evil code is running in ring0, you already lost.

I doubt you can remove all the trampolines, and I do not think you
should uglify the kernel trying to do that.
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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