linux-kernel - Re: [PATCH 0/3] PTI for x86-32 Fixes

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Date:   Thu, 16 Aug 2018 22:44:47 -0400
From:   "David H. Gutteridge" <dhgutteridge@...patico.ca>
To:     Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Juergen Gross <jgross@...e.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>, Jiri Kosina <jkosina@...e.cz>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Brian Gerst <brgerst@...il.com>,
        David Laight <David.Laight@...lab.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Eduardo Valentin <eduval@...zon.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Will Deacon <will.deacon@....com>, aliguori@...zon.com,
        daniel.gruss@...k.tugraz.at, hughd@...gle.com, keescook@...gle.com,
        Andrea Arcangeli <aarcange@...hat.com>,
        Waiman Long <llong@...hat.com>, Pavel Machek <pavel@....cz>,
        jroedel@...e.de
Subject: Re: [PATCH 0/3] PTI for x86-32 Fixes

On Tue, 2018-08-07 at 12:24 +0200, Joerg Roedel wrote:
> Hi,
> 
> here is a small patch-set to fix two small issues in the
> PTI implementation for 32 bit x86. The issues are:
> 
> 	1) Fix the 32 bit PCID check. I used the wrong
> 	   operator there and this caused false-positive
> 	   warnings.
> 
> 	2) The other two patches make sure the init-hole is
> 	   not mapped into the user page-table. It is the
> 	   32 bit counterpart to commit
> 
> 	   c40a56a7818c ('x86/mm/init: Remove freed kernel image areas
> from alias mapping')
> 
> 	   for the 64 bit PTI implementation.
> 
> I tested that no-PAE, PAE and 64 bit kernel all boot and
> have correct user page-tables with identical global mappings
> between user and kernel.
> 
> Regards,
> 
> 	Joerg
> 
> Joerg Roedel (3):
>   x86/mm/pti: Fix 32 bit PCID check
>   x86/mm/pti: Don't clear permissions in pti_clone_pmd()
>   x86/mm/pti: Clone kernel-image on PTE level for 32 bit
> 
>  arch/x86/mm/pti.c | 143 ++++++++++++++++++++++++++++++++++++++-------
> ---------
>  1 file changed, 100 insertions(+), 43 deletions(-)

I've tested this in a VM and on an Atom laptop, as usual. No
regressions noted.

Tested-by: David H. Gutteridge <dhgutteridge@...patico.ca>

Regards,

Dave