linux-kernel - Re: [PATCH v2 5/6] x86/cpu: Remove "noexec"

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Message-ID: <202202071419.E21C67553@keescook>
Date:   Mon, 7 Feb 2022 14:25:44 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
        Lai Jiangshan <jiangshanlai@...il.com>
Subject: Re: [PATCH v2 5/6] x86/cpu: Remove "noexec"

On Thu, Jan 27, 2022 at 12:56:25PM +0100, Borislav Petkov wrote:
> From: Borislav Petkov <bp@...e.de>
> 
> It doesn't make any sense to disable non-executable mappings -
> security-wise or else.
> 
> So rip out that switch and move the remaining code into setup.c and
> delete setup_nx.c
> 
> Signed-off-by: Borislav Petkov <bp@...e.de>
> Reviewed-by: Lai Jiangshan <jiangshanlai@...il.com>

I've dug through the nx fun again. The verify_cpu() calls are untouched
(which were the most fiddly part of all that a decade ago), so that's
good. The early handling of __supported_pte_mask in x86_configure_nx()
is untouched and the call is retained before the param processing for
the set_fixmap() dance, so everything I can remember as being "difficult"
with NX ordering here looks good.

Thanks for cleaning all this up!

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook