Re: [PATCH v3 2/2] arm64/acpi: disallow writeable AML opregion mapping for EFI code regions
From: Shawn Guo <hidden>
Date: 2021-02-06 03:18:45
Also in:
linux-acpi, linux-arm-msm
Hi Ard, On Fri, Jun 26, 2020 at 05:58:32PM +0200, Ard Biesheuvel wrote:
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>
I'm booting Lenovo Flex 5G laptop with ACPI, and seeing this change causes a memory abort[1] when upgrading ACPI tables via initrd[2]. Dropping this change seems to fix the issue for me. But does that looks like a correct fix to you? Shawn [1] https://fileserver.linaro.org/s/iDe9SaZeNNkyNxG [2] Documentation/admin-guide/acpi/initrd_table_override.rst
quoted hunk ↗ jump to hunk
--- arch/arm64/kernel/acpi.c | 9 +++++++++ 1 file changed, 9 insertions(+)diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c index 01b861e225b0..455966401102 100644 --- a/arch/arm64/kernel/acpi.c +++ b/arch/arm64/kernel/acpi.c@@ -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-- 2.27.0
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