linux-kernel - Re: x86/mm: Found insecure W+X mapping at address (ptrval)/0xc00a0000

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Message-ID: <20181004084806.GC1864@zn.tnic>
Date:   Thu, 4 Oct 2018 10:48:06 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Joerg Roedel <joro@...tes.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Paul Menzel <pmenzel@...gen.mpg.de>, linux-mm@...ck.org,
        x86@...nel.org, lkml <linux-kernel@...r.kernel.org>
Subject: Re: x86/mm: Found insecure W+X mapping at address (ptrval)/0xc00a0000

On Thu, Oct 04, 2018 at 10:43:18AM +0200, Joerg Roedel wrote:
> Yeah, that's what I also found out back then, the region needs to be WX.
> So we can either leave with the warning, as we know it is harmless and
> where it comes from or implement an exception in the checking code for
> that region.

The second thing is what I'm thinking too.

Or, a 3rd: not direct-map that first range at all. Commenting out the
ISA range mapping didn't have any adverse effects on my system here, for
example. But then those other mappings appeared:

https://lkml.kernel.org/r/20181003212255.GB28361@zn.tnic

for which I have no explanation yet how they came about.

This needs to be understood fully before we do anything. But it is
32-bit so it gets preempted by more important things all the time :)

-- 
Regards/Gruss,
    Boris.

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