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* [PATCH V34 28/29] efi: Restrict efivar_ssdt_load when the kernel is locked down
       [not found] <20190622000358.19895-1-matthewgarrett@google.com>
@ 2019-06-22  0:03 ` Matthew Garrett
  2019-06-23  0:14   ` Kees Cook
  2019-06-25 15:00   ` Ard Biesheuvel
  0 siblings, 2 replies; 3+ messages in thread
From: Matthew Garrett @ 2019-06-22  0:03 UTC (permalink / raw)
  To: jmorris
  Cc: linux-security-module, linux-kernel, linux-api, Matthew Garrett,
	Matthew Garrett, Ard Biesheuvel, linux-efi

efivar_ssdt_load allows the kernel to import arbitrary ACPI code from an
EFI variable, which gives arbitrary code execution in ring 0. Prevent
that when the kernel is locked down.

Signed-off-by: Matthew Garrett <mjg59@google.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: linux-efi@vger.kernel.org
---
 drivers/firmware/efi/efi.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 55b77c576c42..9f92a013ab27 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -31,6 +31,7 @@
 #include <linux/acpi.h>
 #include <linux/ucs2_string.h>
 #include <linux/memblock.h>
+#include <linux/security.h>
 
 #include <asm/early_ioremap.h>
 
@@ -242,6 +243,11 @@ static void generic_ops_unregister(void)
 static char efivar_ssdt[EFIVAR_SSDT_NAME_MAX] __initdata;
 static int __init efivar_ssdt_setup(char *str)
 {
+	int ret = security_locked_down(LOCKDOWN_ACPI_TABLES);
+
+	if (ret)
+		return ret;
+
 	if (strlen(str) < sizeof(efivar_ssdt))
 		memcpy(efivar_ssdt, str, strlen(str));
 	else
-- 
2.22.0.410.gd8fdbe21b5-goog


^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH V34 28/29] efi: Restrict efivar_ssdt_load when the kernel is locked down
  2019-06-22  0:03 ` [PATCH V34 28/29] efi: Restrict efivar_ssdt_load when the kernel is locked down Matthew Garrett
@ 2019-06-23  0:14   ` Kees Cook
  2019-06-25 15:00   ` Ard Biesheuvel
  1 sibling, 0 replies; 3+ messages in thread
From: Kees Cook @ 2019-06-23  0:14 UTC (permalink / raw)
  To: Matthew Garrett
  Cc: jmorris, linux-security-module, linux-kernel, linux-api,
	Matthew Garrett, Ard Biesheuvel, linux-efi

On Fri, Jun 21, 2019 at 05:03:57PM -0700, Matthew Garrett wrote:
> efivar_ssdt_load allows the kernel to import arbitrary ACPI code from an
> EFI variable, which gives arbitrary code execution in ring 0. Prevent
> that when the kernel is locked down.
> 
> Signed-off-by: Matthew Garrett <mjg59@google.com>

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

-Kees

> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: linux-efi@vger.kernel.org
> ---
>  drivers/firmware/efi/efi.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> index 55b77c576c42..9f92a013ab27 100644
> --- a/drivers/firmware/efi/efi.c
> +++ b/drivers/firmware/efi/efi.c
> @@ -31,6 +31,7 @@
>  #include <linux/acpi.h>
>  #include <linux/ucs2_string.h>
>  #include <linux/memblock.h>
> +#include <linux/security.h>
>  
>  #include <asm/early_ioremap.h>
>  
> @@ -242,6 +243,11 @@ static void generic_ops_unregister(void)
>  static char efivar_ssdt[EFIVAR_SSDT_NAME_MAX] __initdata;
>  static int __init efivar_ssdt_setup(char *str)
>  {
> +	int ret = security_locked_down(LOCKDOWN_ACPI_TABLES);
> +
> +	if (ret)
> +		return ret;
> +
>  	if (strlen(str) < sizeof(efivar_ssdt))
>  		memcpy(efivar_ssdt, str, strlen(str));
>  	else
> -- 
> 2.22.0.410.gd8fdbe21b5-goog
> 

-- 
Kees Cook

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH V34 28/29] efi: Restrict efivar_ssdt_load when the kernel is locked down
  2019-06-22  0:03 ` [PATCH V34 28/29] efi: Restrict efivar_ssdt_load when the kernel is locked down Matthew Garrett
  2019-06-23  0:14   ` Kees Cook
@ 2019-06-25 15:00   ` Ard Biesheuvel
  1 sibling, 0 replies; 3+ messages in thread
From: Ard Biesheuvel @ 2019-06-25 15:00 UTC (permalink / raw)
  To: Matthew Garrett
  Cc: James Morris, linux-security-module, Linux Kernel Mailing List,
	linux-api, Matthew Garrett, linux-efi

On Sat, 22 Jun 2019 at 02:05, Matthew Garrett <matthewgarrett@google.com> wrote:
>
> efivar_ssdt_load allows the kernel to import arbitrary ACPI code from an
> EFI variable, which gives arbitrary code execution in ring 0. Prevent
> that when the kernel is locked down.
>
> Signed-off-by: Matthew Garrett <mjg59@google.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: linux-efi@vger.kernel.org

Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

> ---
>  drivers/firmware/efi/efi.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> index 55b77c576c42..9f92a013ab27 100644
> --- a/drivers/firmware/efi/efi.c
> +++ b/drivers/firmware/efi/efi.c
> @@ -31,6 +31,7 @@
>  #include <linux/acpi.h>
>  #include <linux/ucs2_string.h>
>  #include <linux/memblock.h>
> +#include <linux/security.h>
>
>  #include <asm/early_ioremap.h>
>
> @@ -242,6 +243,11 @@ static void generic_ops_unregister(void)
>  static char efivar_ssdt[EFIVAR_SSDT_NAME_MAX] __initdata;
>  static int __init efivar_ssdt_setup(char *str)
>  {
> +       int ret = security_locked_down(LOCKDOWN_ACPI_TABLES);
> +
> +       if (ret)
> +               return ret;
> +
>         if (strlen(str) < sizeof(efivar_ssdt))
>                 memcpy(efivar_ssdt, str, strlen(str));
>         else
> --
> 2.22.0.410.gd8fdbe21b5-goog
>

^ permalink raw reply	[flat|nested] 3+ messages in thread

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Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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     [not found] <20190622000358.19895-1-matthewgarrett@google.com>
2019-06-22  0:03 ` [PATCH V34 28/29] efi: Restrict efivar_ssdt_load when the kernel is locked down Matthew Garrett
2019-06-23  0:14   ` Kees Cook
2019-06-25 15:00   ` Ard Biesheuvel

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