linux-kernel - Re: [patch V163 02/51] x86/vsyscall/64: Explicitly set _PAGE

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Date:   Mon, 18 Dec 2017 15:21:13 +0100
From:   Borislav Petkov <bp@...e.de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirsky <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Greg KH <gregkh@...uxfoundation.org>, keescook@...gle.com,
        hughd@...gle.com, Brian Gerst <brgerst@...il.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Rik van Riel <riel@...hat.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        David Laight <David.Laight@...lab.com>,
        Eduardo Valentin <eduval@...zon.com>, aliguori@...zon.com,
        Will Deacon <will.deacon@....com>, daniel.gruss@...k.tugraz.at,
        Ingo Molnar <mingo@...nel.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [patch V163 02/51] x86/vsyscall/64: Explicitly set _PAGE_USER in
 the pagetable hierarchy

On Mon, Dec 18, 2017 at 12:42:17PM +0100, Thomas Gleixner wrote:
> From: Andy Lutomirski <luto@...nel.org>
> 
> The kernel is very erratic as to which pagetables have _PAGE_USER set.  The
> vsyscall page gets lucky: it seems that all of the relevant pagetables are
> among the apparently arbitrary ones that set _PAGE_USER.  Rather than
> relying on chance, just explicitly set _PAGE_USER.
> 
> This will let us clean up pagetable setup to stop setting _PAGE_USER.  The
> added code can also be reused by pagetable isolation to manage the
> _PAGE_USER bit in the usermode tables.
> 
> Signed-off-by: Andy Lutomirski <luto@...nel.org>
> Signed-off-by: Ingo Molnar <mingo@...nel.org>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Brian Gerst <brgerst@...il.com>
> Cc: David Laight <David.Laight@...lab.com>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> ---
>  arch/x86/entry/vsyscall/vsyscall_64.c |   33 ++++++++++++++++++++++++++++++++-
>  1 file changed, 32 insertions(+), 1 deletion(-)

Nice.

Reviewed-by: Borislav Petkov <bp@...e.de>

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
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