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 when upgrading ACPI tables via initrd. Dropping this change seems to fix the issue for me. But does that looks like a correct fix to you? Shawn  https://fileserver.linaro.org/s/iDe9SaZeNNkyNxG  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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