Re: [PATCH V34 28/29] efi: Restrict efivar_ssdt_load when the kernel is locked down

[Ard Biesheuvel]

On Sat, 22 Jun 2019 at 02:05, 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 
> Cc: Ard Biesheuvel 
> Cc: linux-efi@vger.kernel.org

Acked-by: Ard Biesheuvel 

> ---
>  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 
>  #include 
>  #include 
> +#include 
>
>  #include 
>
> @@ -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
>

Re: [PATCH V34 28/29] efi: Restrict efivar_ssdt_load when the kernel is locked down

[Kees Cook]

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 

Reviewed-by: Kees Cook 

-Kees

> Cc: Ard Biesheuvel 
> 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 
>  #include 
>  #include 
> +#include 
>  
>  #include 
>  
> @@ -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

[PATCH V34 28/29] efi: Restrict efivar_ssdt_load when the kernel is locked down

[Matthew Garrett]

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 
Cc: Ard Biesheuvel 
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 
 #include 
 #include 
+#include 
 
 #include 
 
@@ -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