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Commit 04178b17 authored by Matthew Garrett's avatar Matthew Garrett Committed by Greg Kroah-Hartman
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x86/efi: Clarify that reset attack mitigation needs appropriate userspace 



commit a5c03c31af2291f13689d11760c0b59fb70c9a5a upstream.

Some distributions have turned on the reset attack mitigation feature,
which is designed to force the platform to clear the contents of RAM if
the machine is shut down uncleanly. However, in order for the platform
to be able to determine whether the shutdown was clean or not, userspace
has to be configured to clear the MemoryOverwriteRequest flag on
shutdown - otherwise the firmware will end up clearing RAM on every
reboot, which is unnecessarily time consuming. Add some additional
clarity to the kconfig text to reduce the risk of systems being
configured this way.

Signed-off-by: default avatarMatthew Garrett <mjg59@google.com>
Acked-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 01ab9886

drivers/firmware/efi/Kconfig

+4 −1
Original line number Diff line number Diff line
@@ -159,7 +159,10 @@ config RESET_ATTACK_MITIGATION 
	  using the TCG Platform Reset Attack Mitigation specification. This

	  protects against an attacker forcibly rebooting the system while it

	  still contains secrets in RAM, booting another OS and extracting the

	  secrets.

	  secrets. This should only be enabled when userland is configured to

	  clear the MemoryOverwriteRequest flag on clean shutdown after secrets

	  have been evicted, since otherwise it will trigger even on clean

	  reboots.



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