Date: Sat, 6 Feb 2021 11:17:57 +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 09:10, Ard Biesheuvel <ardb@...nel.org> wrote: > > 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. > That patch modifies firmware provided tables in-place, which invalidates checksums and TPM measurements, so it needs to be reverted in any case, and I have already sent out the patch for doing so.
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