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Re: [PATCHv4 09/10] mm/usercopy: Switch to using lm_alias

From Mark Rutland <mark.rutland@arm.com>
Newsgroups linux.kernel
Subject Re: [PATCHv4 09/10] mm/usercopy: Switch to using lm_alias
Date 2016-12-06 19:30 +0100
Message-ID <sLsF4-5D5-13@gated-at.bofh.it> (permalink)
References <sIVNf-3Mq-3@gated-at.bofh.it> <sIVNg-3Mq-37@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Tue, Nov 29, 2016 at 10:55:28AM -0800, Laura Abbott wrote:
> 
> The usercopy checking code currently calls __va(__pa(...)) to check for
> aliases on symbols. Switch to using lm_alias instead.
> 
> Signed-off-by: Laura Abbott <labbott@redhat.com>

I've given this a go on Juno, which boots happily. LKDTM triggers as
expected when copying from the kernel text and its alias.

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>

Thanks,
Mark.

> ---
> Found when reviewing the kernel. Tested.
> ---
>  mm/usercopy.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/usercopy.c b/mm/usercopy.c
> index 3c8da0a..8345299 100644
> --- a/mm/usercopy.c
> +++ b/mm/usercopy.c
> @@ -108,13 +108,13 @@ static inline const char *check_kernel_text_object(const void *ptr,
>  	 * __pa() is not just the reverse of __va(). This can be detected
>  	 * and checked:
>  	 */
> -	textlow_linear = (unsigned long)__va(__pa(textlow));
> +	textlow_linear = (unsigned long)lm_alias(textlow);
>  	/* No different mapping: we're done. */
>  	if (textlow_linear == textlow)
>  		return NULL;
>  
>  	/* Check the secondary mapping... */
> -	texthigh_linear = (unsigned long)__va(__pa(texthigh));
> +	texthigh_linear = (unsigned long)lm_alias(texthigh);
>  	if (overlaps(ptr, n, textlow_linear, texthigh_linear))
>  		return "<linear kernel text>";
>  
> -- 
> 2.7.4
> 

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Thread

[PATCHv4 00/10] CONFIG_DEBUG_VIRTUAL for arm64 Laura Abbott <labbott@redhat.com> - 2016-11-29 20:00 +0100
  [PATCHv4 09/10] mm/usercopy: Switch to using lm_alias Laura Abbott <labbott@redhat.com> - 2016-11-29 20:00 +0100
    Re: [PATCHv4 09/10] mm/usercopy: Switch to using lm_alias Kees Cook <keescook@chromium.org> - 2016-11-29 20:40 +0100
      Re: [PATCHv4 09/10] mm/usercopy: Switch to using lm_alias Mark Rutland <mark.rutland@arm.com> - 2016-12-06 19:20 +0100
        Re: [PATCHv4 09/10] mm/usercopy: Switch to using lm_alias Kees Cook <keescook@chromium.org> - 2016-12-06 21:20 +0100
          Re: [PATCHv4 09/10] mm/usercopy: Switch to using lm_alias Mark Rutland <mark.rutland@arm.com> - 2016-12-07 15:00 +0100
    Re: [PATCHv4 09/10] mm/usercopy: Switch to using lm_alias Mark Rutland <mark.rutland@arm.com> - 2016-12-06 19:30 +0100
  [PATCHv4 10/10] arm64: Add support for CONFIG_DEBUG_VIRTUAL Laura Abbott <labbott@redhat.com> - 2016-11-29 20:00 +0100
    Re: [PATCHv4 10/10] arm64: Add support for CONFIG_DEBUG_VIRTUAL Mark Rutland <mark.rutland@arm.com> - 2016-12-06 20:00 +0100
  [PATCHv4 08/10] mm/kasan: Switch to using __pa_symbol and lm_alias Laura Abbott <labbott@redhat.com> - 2016-11-29 20:00 +0100
    Re: [PATCHv4 08/10] mm/kasan: Switch to using __pa_symbol and  lm_alias Laura Abbott <labbott@redhat.com> - 2016-12-01 20:20 +0100
    Re: [PATCHv4 08/10] mm/kasan: Switch to using __pa_symbol and  lm_alias Mark Rutland <mark.rutland@arm.com> - 2016-12-06 18:30 +0100
    Re: [PATCHv4 08/10] mm/kasan: Switch to using __pa_symbol and  lm_alias Mark Rutland <mark.rutland@arm.com> - 2016-12-06 18:50 +0100
    Re: [PATCHv4 08/10] mm/kasan: Switch to using __pa_symbol and  lm_alias Mark Rutland <mark.rutland@arm.com> - 2016-12-06 20:30 +0100
  [PATCHv4 06/10] xen: Switch to using __pa_symbol Laura Abbott <labbott@redhat.com> - 2016-11-29 20:00 +0100
    Re: [PATCHv4 06/10] xen: Switch to using __pa_symbol Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-11-29 23:30 +0100
      Re: [PATCHv4 06/10] xen: Switch to using __pa_symbol Laura Abbott <labbott@redhat.com> - 2016-11-29 23:50 +0100
  [PATCH 0/3] ARM: Add support for CONFIG_DEBUG_VIRTUAL Florian Fainelli <f.fainelli@gmail.com> - 2016-12-06 21:00 +0100
    [PATCH 3/3] ARM: Add support for CONFIG_DEBUG_VIRTUAL Florian Fainelli <f.fainelli@gmail.com> - 2016-12-06 21:00 +0100
      Re: [PATCH 3/3] ARM: Add support for CONFIG_DEBUG_VIRTUAL Florian Fainelli <f.fainelli@gmail.com> - 2016-12-06 21:50 +0100
      Re: [PATCH 3/3] ARM: Add support for CONFIG_DEBUG_VIRTUAL Laura Abbott <labbott@redhat.com> - 2016-12-07 03:10 +0100
        Re: [PATCH 3/3] ARM: Add support for CONFIG_DEBUG_VIRTUAL Florian Fainelli <f.fainelli@gmail.com> - 2016-12-07 03:30 +0100
    [PATCH 2/3] ARM: Utilize __pa_symbol in lieu of __pa Florian Fainelli <f.fainelli@gmail.com> - 2016-12-06 21:00 +0100
    [PATCH 1/3] ARM: Define KERNEL_START and KERNEL_END Florian Fainelli <f.fainelli@gmail.com> - 2016-12-06 21:00 +0100
      Re: [PATCH 1/3] ARM: Define KERNEL_START and KERNEL_END Florian Fainelli <f.fainelli@gmail.com> - 2016-12-06 23:50 +0100
      RE: [PATCH 1/3] ARM: Define KERNEL_START and KERNEL_END Chris Brandt <Chris.Brandt@renesas.com> - 2016-12-06 23:50 +0100
      Re: [PATCH 1/3] ARM: Define KERNEL_START and KERNEL_END kbuild test robot <lkp@intel.com> - 2016-12-07 07:20 +0100

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