Date: Sat, 26 Feb 2011 04:58:06 +0100
From: Pavel Machek <pavel@ucw.cz>
To: matthieu castet <castet.matthieu@free.fr>
Cc: "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@elte.hu>,
        Linux Kernel list <linux-kernel@vger.kernel.org>,
        linux-security-module@vger.kernel.org, Matthias Hopf <mhopf@suse.de>,
        rjw@sisk.pl, Andrew Morton <akpm@linux-foundation.org>,
        Suresh Siddha <suresh.b.siddha@intel.com>
Subject: Re: [PATCH] NX protection for kernel data : fix 32 bits S3 suspend
Message-ID: <20110226035805.GA1656@ucw.cz>
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On Sat 2011-02-12 17:10:14, matthieu castet wrote:
> H. Peter Anvin a ?crit :
> >On 02/07/2011 11:59 AM, castet.matthieu@free.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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