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efi/libstub: Enable reset attack mitigation

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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 <mjg59@google.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/20170825155019.6740-2-ard.biesheuvel@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Matthew Garrett
2017-08-25 16:50:15 +01:00
committed by Ingo Molnar
parent 3cb9bc8502
commit ccc829ba36
6 changed files with 82 additions and 0 deletions
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3
drivers/firmware/efi/libstub/arm-stub.c
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@@ -192,6 +192,9 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table,
goto fail_free_cmdline;
}
/* Ask the firmware to clear memory on unclean shutdown */
efi_enable_reset_attack_mitigation(sys_table);
secure_boot = efi_get_secureboot(sys_table);
/*