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Date:   Thu, 9 Aug 2018 13:16:03 +0200
From:   Joerg Roedel <jroedel@suse.de>
To:     Dave Hansen <dave.hansen@intel.com>
Cc:     Joerg Roedel <joro@8bytes.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@kernel.org>,
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        Waiman Long <llong@redhat.com>, Pavel Machek <pavel@ucw.cz>,
        "David H . Gutteridge" <dhgutteridge@sympatico.ca>
Subject: Re: [PATCH] x86/mm/pti: Move user W+X check into pti_finalize()
Message-ID: <20180809111603.aqon7xqmanvoycbu@suse.de>
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Hi Dave,

On Wed, Aug 08, 2018 at 08:54:37AM -0700, Dave Hansen wrote:
> One bit of information missing from the changelog: Could you clarify how
> there are any entries in the user page tables for the code to complain?
> Before pti_init(), I would have expected the user page tables to be empty.

The W+X check runs at the end of mark_readonly() in x86, which is after
pti_init() already put kernel mappings into the user page-table. Problem
is that the cloned entries are still W+X mapped, which is fixed in
pti_finalize() running _after_ mark_readonly().

Regards,

	Joerg