linux-kernel - Re: [PATCH 07/12] acpi: Ignore acpi_rsdp kernel parameter when securelevel is set

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Message-ID: <CA+5PVA6_4o6T7gS7q5uvksUBawxV__J82KQBMC=hE_qdTK2RUA@mail.gmail.com>
Date:	Tue, 26 Nov 2013 07:54:23 -0500
From:	Josh Boyer <jwboyer@...hat.com>
To:	Matthew Garrett <matthew.garrett@...ula.com>
Cc:	"Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
	Kees Cook <keescook@...omium.org>,
	Greg KH <gregkh@...uxfoundation.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	James Morris <jmorris@...ei.org>,
	linux-security-module <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH 07/12] acpi: Ignore acpi_rsdp kernel parameter when
 securelevel is set

On Mon, Sep 9, 2013 at 11:49 AM, Matthew Garrett
<matthew.garrett@...ula.com> wrote:
> From: Josh Boyer <jwboyer@...hat.com>
>
> This option allows userspace to pass the RSDP address to the kernel, which
> makes it possible for a user to execute arbitrary code in the kernel.
> Disable this when securelevel is set.
>
> Signed-off-by: Josh Boyer <jwboyer@...hat.com>

Dredging up an old thread in the hopes that Matthew runs sed and resubmits...

Also, FWIW, I didn't write this.  It was derived from previous
versions of something I did write, but there's really no evidence of
anything I wrote left, so it should probably be From: you.

> ---
>  drivers/acpi/osl.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
> index e5f416c..f6d8977 100644
> --- a/drivers/acpi/osl.c
> +++ b/drivers/acpi/osl.c
> @@ -45,6 +45,7 @@
>  #include <linux/list.h>
>  #include <linux/jiffies.h>
>  #include <linux/semaphore.h>
> +#include <linux/security.h>
>
>  #include <asm/io.h>
>  #include <asm/uaccess.h>
> @@ -249,7 +250,7 @@ early_param("acpi_rsdp", setup_acpi_rsdp);
>  acpi_physical_address __init acpi_os_get_root_pointer(void)
>  {
>  #ifdef CONFIG_KEXEC
> -       if (acpi_rsdp)
> +       if (acpi_rsdp && (get_securelevel <= 0))

This is missing some ( ).  That means you're comparing the
get_securelevel function pointer to 0.  Pretty sure bad things will
happen.

josh
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