Date: Sat, 6 Feb 2021 09:10:19 +0100 From: Ard Biesheuvel <ardb@...nel.org> To: Shawn Guo <shawn.guo@...aro.org> Cc: Linux ARM <linux-arm-kernel@...ts.infradead.org>, Lorenzo Pieralisi <lorenzo.pieralisi@....com>, Kernel Hardening <kernel-hardening@...ts.openwall.com>, Catalin Marinas <catalin.marinas@....com>, ACPI Devel Maling List <linux-acpi@...r.kernel.org>, Sudeep Holla <sudeep.holla@....com>, Will Deacon <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 On Sat, 6 Feb 2021 at 04:11, Shawn Guo <shawn.guo@...aro.org> wrote: > > 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 > Can you check whether reverting 32cf1a12cad43358e47dac8014379c2f33dfbed4 fixes the issue too? If it does, please report this as a regression. The OS should not modify firmware provided tables in-place, regardless of how they were delivered. BTW I recently started using my Yoga C630 with Debian, and I am quite happy with it! Thanks a lot for spending the time on the installer etc. I have observed some issues while using mine - I'm happy to share them, on a mailing list or anywhere else. > > --- > > 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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