From ccc829ba3624beb9a703fc995d016b836d9eead8 Mon Sep 17 00:00:00 2001 From: Matthew Garrett Date: Fri, 25 Aug 2017 16:50:15 +0100 Subject: efi/libstub: Enable reset attack mitigation If a machine is reset while secrets are present in RAM, it may be possible for code executed after the reboot to extract those secrets from untouched memory. The Trusted Computing Group specified a mechanism for requesting that the firmware clear all RAM on reset before booting another OS. This is done by setting the MemoryOverwriteRequestControl variable at startup. If userspace can ensure that all secrets are removed as part of a controlled shutdown, it can reset this variable to 0 before triggering a hardware reboot. Signed-off-by: Matthew Garrett Signed-off-by: Ard Biesheuvel Cc: Linus Torvalds Cc: Matt Fleming Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-efi@vger.kernel.org Link: http://lkml.kernel.org/r/20170825155019.6740-2-ard.biesheuvel@linaro.org Signed-off-by: Ingo Molnar --- arch/x86/boot/compressed/eboot.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'arch/x86/boot') diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c index c3e869eaef0c..a1686f3dc295 100644 --- a/arch/x86/boot/compressed/eboot.c +++ b/arch/x86/boot/compressed/eboot.c @@ -997,6 +997,9 @@ struct boot_params *efi_main(struct efi_config *c, if (boot_params->secure_boot == efi_secureboot_mode_unset) boot_params->secure_boot = efi_get_secureboot(sys_table); + /* Ask the firmware to clear memory on unclean shutdown */ + efi_enable_reset_attack_mitigation(sys_table); + setup_graphics(boot_params); setup_efi_pci(boot_params); -- cgit