linux-kernel - Re: [RFC][PATCH 04/10] x86/espfix: use kernel-default PTE mask

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Message-ID: <8fca2faa-1bac-2252-3719-8d393e2f2661@linux.intel.com>
Date:   Thu, 22 Feb 2018 14:05:19 -0800
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Nadav Amit <namit@...are.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "aarcange@...hat.com" <aarcange@...hat.com>,
        "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
        "keescook@...gle.com" <keescook@...gle.com>,
        "hughd@...gle.com" <hughd@...gle.com>,
        "jgross@...e.com" <jgross@...e.com>,
        "x86@...nel.org" <x86@...nel.org>
Subject: Re: [RFC][PATCH 04/10] x86/espfix: use kernel-default PTE mask

On 02/22/2018 01:59 PM, Andy Lutomirski wrote:
>> I think it's good practice to just expose only the *minimal* amount of
>> data necessary.  It's easier to audit and less likely to expose things
>> accidentall.
> But espfix64 is geniunely global.  I'm confused.

I'm the confused one.

In my *first* set of patches to do this, I missed making the espfix64
area global.  This new code apparently got it right, but I assumed the
"new" global area that showed up was a mistake, thus this patch.

I'll change this patch into a commenting patch that calls out the need
for keeping _PAGE_GLOBAL.