linux-kernel - Re: [PATCH] x86/ldt: Fix support_pte_mask filtering in map_ldt

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Date:   Thu, 19 Apr 2018 12:22:40 -0700
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     Joerg Roedel <joro@...tes.org>, Borislav Petkov <bp@...e.de>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <jroedel@...e.de>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>
Subject: Re: [PATCH] x86/ldt: Fix support_pte_mask filtering in
 map_ldt_struct()

On 04/19/2018 07:11 AM, Joerg Roedel wrote:
> On Thu, Apr 19, 2018 at 03:00:11PM +0200, Borislav Petkov wrote:
>> fb43d6cb91ef x86/mm: Do not auto-massage page protections <--- NOT OK
> Hmm, that hunk from above patch looks suspicious:
> 
> -               set_pgd(pgd + pgd_index(restore_jump_address), __pgd(__pa(pud) | _KERNPG_TABLE));
> +               pgd_t new_pgd = __pgd(__pa(p4d) | pgprot_val(pgtable_prot));
> +               set_pgd(pgd + pgd_index(restore_jump_address), new_pgd);
> 
> The old code used __pa(pud) while the new one uses __pa(p4d).
> 
> Boris, can you change that back to __pa(pud) and test please?

That does look like the culprit.  I probably copy/pasted the p4d line
from above and missed that 'p4d' when converting it to pud.

Thanks for finding this, guys.