On Jun 19, 2011, at 4:11 PM, AK <platsakos (at) gmail (dot) com [email concealed]> wrote:
> while I agree with the 2nd paragraph of the email Paul wrote, I believe
> that a small clarification should be made on the 1st paragraph. In x86,
> the NX bit can be emulated. Emulating the NX bit causes certain
> processors to fail to boot, although we are talking K6s/PentiumMMX era
> CPUs IIRC. Thus for all intents and purposes, NX-bit can be reliably
> emulated in modern x86 CPUs.

I think it's present and available for PAE memory addressing in all modern x86 CPUs. And yes, some kernels are able to emulate it in 32-bit modes as well. I think this illustrates my point (and yours) that exploitability of a vulnerability across platforms is about nuance. And it's additionally safe to say that exploitability has changed significantly in the last 5 years both within and across all modern platforms.

PaulM

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