Commit 325f5585 authored Jun 26, 2020 by Ard Biesheuvel Committed by Catalin Marinas Jul 14, 2020

arm64/acpi: disallow writeable AML opregion mapping for EFI code regions

Given that the contents of EFI runtime code and data regions are
provided by the firmware, as well as the DSDT, it is not unimaginable
that AML code exists today that accesses EFI runtime code regions using
a SystemMemory OpRegion. There is nothing fundamentally wrong with that,
but since we take great care to ensure that executable code is never
mapped writeable and executable at the same time, we should not permit
AML to create writable mapping.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Link: https://lore.kernel.org/r/20200626155832.2323789-3-ardb@kernel.org

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

parent 1583052d

arch/arm64/kernel/acpi.c

+9 −0

Original line number	Diff line number	Diff line
		@@ -301,6 +301,15 @@ void __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size)
		pr_warn(FW_BUG "requested region covers kernel memory @ %pa\n", &phys);
		return NULL;

		case EFI_RUNTIME_SERVICES_CODE:
		/*
		* This would be unusual, but not problematic per se,
		* as long as we take care not to create a writable
		* mapping for executable code.
		*/
		prot = PAGE_KERNEL_RO;
		break;

		case EFI_ACPI_RECLAIM_MEMORY:
		/*
		* ACPI reclaim memory is used to pass firmware tables