linux-kernel - Re: [PATCH] x86: Zero-pad the VVAR page with zeros

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Message-ID: <CALCETrWa2dzLNChxVO83-OHFmxn74tAxdAjAqG3B_33nHaCAZQ@mail.gmail.com>
Date:	Fri, 31 Jan 2014 15:05:34 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	X86 ML <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:	Andy Lutomirski <luto@...capital.net>
Subject: Re: [PATCH] x86: Zero-pad the VVAR page with zeros

*sigh*.  Feel free to make the subject less dumb if you apply this.

--Andy

On Fri, Jan 31, 2014 at 3:04 PM, Andy Lutomirski <luto@...capital.net> wrote:
>
> This has probably been broken since the VVAR page was introduced.
> The symptom is that BIOS crud can be left behind where userspace can
> see it.  (I saw this with QEMU.)
>
> Signed-off-by: Andy Lutomirski <luto@...capital.net>
> ---
>  arch/x86/kernel/vmlinux.lds.S | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
> index da6b35a..331a66f 100644
> --- a/arch/x86/kernel/vmlinux.lds.S
> +++ b/arch/x86/kernel/vmlinux.lds.S
> @@ -165,6 +165,11 @@ SECTIONS
>  #undef __VVAR_KERNEL_LDS
>  #undef EMIT_VVAR
>
> +               /*
> +                * Pad the rest of the page with zeros.  Otherwise the loader
> +                * can leave garbage here.
> +                */
> +               . = __vvar_beginning_hack + PAGE_SIZE;
>         } :data
>
>         . = ALIGN(__vvar_page + PAGE_SIZE, PAGE_SIZE);
> --
> 1.8.5.3
>



-- 
Andy Lutomirski
AMA Capital Management, LLC
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