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

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On Tue, Nov 29, 2016 at 10:55 AM, Laura Abbott <labbott@redhat.com> 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>

Acked-by: Kees Cook <keescook@chromium.org>

I should probably add a corresponding alias test to lkdtm...

-Kees

> ---
> 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
>



-- 
Kees Cook
Nexus Security

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[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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