From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Garrett Subject: [PATCH V40 28/29] efi: Restrict efivar_ssdt_load when the kernel is locked down Date: Mon, 19 Aug 2019 17:18:04 -0700 Message-ID: <20190820001805.241928-29-matthewgarrett@google.com> References: <20190820001805.241928-1-matthewgarrett@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: <20190820001805.241928-1-matthewgarrett@google.com> Sender: linux-kernel-owner@vger.kernel.org To: jmorris@namei.org Cc: linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Matthew Garrett , Matthew Garrett , Ard Biesheuvel , Kees Cook , linux-efi@vger.kernel.org List-Id: linux-api@vger.kernel.org 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 Acked-by: Ard Biesheuvel Reviewed-by: Kees Cook Cc: Ard Biesheuvel Cc: linux-efi@vger.kernel.org Signed-off-by: James Morris --- 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 4b7cf7bc0ded..5f98374f77f4 100644 --- a/drivers/firmware/efi/efi.c +++ b/drivers/firmware/efi/efi.c @@ -30,6 +30,7 @@ #include #include #include +#include #include @@ -241,6 +242,11 @@ 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 -- 2.23.0.rc1.153.gdeed80330f-goog