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Date: Sat, 6 Feb 2021 11:11:46 +0800
From: Shawn Guo <shawn.guo@...aro.org>
To: Ard Biesheuvel <ardb@...nel.org>
Cc: linux-arm-kernel@...ts.infradead.org, lorenzo.pieralisi@....com,
kernel-hardening@...ts.openwall.com, catalin.marinas@....com,
linux-acpi@...r.kernel.org, sudeep.holla@....com, will@...nel.org,
linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v3 2/2] arm64/acpi: disallow writeable AML opregion
mapping for EFI code regions
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@...nel.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
> ---
> 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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