linux-kernel - Re: [PATCH 01/30] x86, mm: do not set _PAGE_USER for init

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Date:   Thu, 9 Nov 2017 11:29:25 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Dave Hansen <dave.hansen@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        tglx@...utronix.de, moritz.lipp@...k.tugraz.at,
        daniel.gruss@...k.tugraz.at, michael.schwarz@...k.tugraz.at,
        richard.fellner@...dent.tugraz.at, luto@...nel.org,
        torvalds@...ux-foundation.org, keescook@...gle.com,
        hughd@...gle.com, x86@...nel.org
Subject: Re: [PATCH 01/30] x86, mm: do not set _PAGE_USER for init_mm page
 tables

On Wed, Nov 08, 2017 at 11:46:47AM -0800, Dave Hansen wrote:
> 
> From: Dave Hansen <dave.hansen@...ux.intel.com>
> 
> init_mm is for kernel-exclusive use.  If someone is allocating page
> tables for it, do not set _PAGE_USER on them.
> 
> Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
> Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
> Cc: Moritz Lipp <moritz.lipp@...k.tugraz.at>
> Cc: Daniel Gruss <daniel.gruss@...k.tugraz.at>
> Cc: Michael Schwarz <michael.schwarz@...k.tugraz.at>
> Cc: Richard Fellner <richard.fellner@...dent.tugraz.at>
> Cc: Andy Lutomirski <luto@...nel.org>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Kees Cook <keescook@...gle.com>
> Cc: Hugh Dickins <hughd@...gle.com>
> Cc: x86@...nel.org
> ---
> 
>  b/arch/x86/include/asm/pgalloc.h |   33 ++++++++++++++++++++++++++++-----
>  1 file changed, 28 insertions(+), 5 deletions(-)
> 
> diff -puN arch/x86/include/asm/pgalloc.h~kaiser-prep-clear-_PAGE_USER-for-init_mm arch/x86/include/asm/pgalloc.h
> --- a/arch/x86/include/asm/pgalloc.h~kaiser-prep-clear-_PAGE_USER-for-init_mm	2017-11-08 10:45:25.928681403 -0800
> +++ b/arch/x86/include/asm/pgalloc.h	2017-11-08 10:45:25.931681403 -0800
> @@ -61,20 +61,37 @@ static inline void __pte_free_tlb(struct
>  	___pte_free_tlb(tlb, pte);
>  }
>  
> +/*
> + * init_mm is for kernel-exclusive use.  Any page tables that
> + * are seteup for it should not be usable by userspace.

s/seteup/setup/

-- 
Regards/Gruss,
    Boris.

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