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

[Pavel Machek <pavel@ucw.cz>]

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@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
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