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Refactor CPU mitigations

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raja-grewal 2024-12-17 11:42:03 +00:00 committed by GitHub
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etc/default/grub.d/40_cpu_mitigations.cfg
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@ -17,7 +17,7 @@
## https://www.intel.com/content/www/us/en/developer/topic-technology/software-security-guidance/advisory-guidance.html
## https://www.intel.com/content/www/us/en/developer/topic-technology/software-security-guidance/disclosure-documentation.html
## Enable a subset of known mitigations for CPU vulnerabilities and disable SMT.
## Enable a subset of known mitigations for some CPU vulnerabilities and disable SMT.
##
## KSPP=yes
## KSPP sets the kernel parameters.
@ -27,7 +27,7 @@ GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX mitigations=auto,nosmt"
## Disable SMT as it has been the cause of and amplified numerous CPU exploits.
## The only full mitigation of cross-HT attacks is to disable SMT.
## Disabling will significantly decrease system performance on multi-threaded tasks.
## To enable SMT, remove this line and all other occurrences of "nosmt" in this file.
## Note, this setting will prevent re-enabling SMT via the sysfs interface.
##
## https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/core-scheduling.html
## https://forums.whonix.org/t/should-all-kernel-patches-for-cpu-bugs-be-unconditionally-enabled-vs-performance-vs-applicability/7647/17
@ -36,95 +36,125 @@ GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX mitigations=auto,nosmt"
## KSPP=yes
## KSPP sets the kernel parameter.
##
## To re-enable SMT:
## - Remove "nosmt=force".
## - Remove all occurrences of ",nosmt" in this file (note the comma ",").
## - Downgrade "l1tf=full,force" protection to "l1tf=flush".
##
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX nosmt=force"
## Enable mitigations for both Spectre Variant 2 (indirect branch speculation)
## and Intel branch history injection (BHI) vulnerabilities.
## Spectre Side Channels (BTI and BHI):
## Unconditionally enable mitigation for Spectre Variant 2 (branch target injection).
## Enable mitigation for the Intel branch history injection vulnerability.
## Currently affects both AMD and Intel CPUs.
##
## https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/spectre.html
##
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX spectre_v2=on"
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX spectre_bhi=on"
## Disable Speculative Store Bypass (Spectre Variant 4).
## Unconditionally enable mitigation for both kernel and userspace.
## Speculative Store Bypass (SSB):
## Mitigate Spectre Variant 4 by disabling speculative store bypass system-wide.
## Unconditionally enable the mitigation for both kernel and userspace.
## Currently affects both AMD and Intel CPUs.
##
## https://en.wikipedia.org/wiki/Speculative_Store_Bypass
## https://www.suse.com/support/kb/doc/?id=000019189
##
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX spec_store_bypass_disable=on"
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX ssbd=force-on"
## Enable mitigations for the L1TF vulnerability through disabling SMT
## and L1D flush runtime control.
## L1 Terminal Fault (L1TF):
## Mitigate the vulnerability by disabling L1D flush runtime control and SMT.
## Currently affects Intel CPUs.
##
## https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html
##
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX l1tf=full,force"
## Enable mitigations for the MDS vulnerability through clearing buffer cache
## and disabling SMT.
## Microarchitectural Data Sampling (MDS):
## Mitigate the vulnerability by clearing the buffer cache and disabling SMT.
## Currently affects Intel CPUs.
##
## https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/mds.html
##
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX mds=full,nosmt"
## Patches the TAA vulnerability by disabling TSX and enables mitigations using
## TSX Async Abort along with disabling SMT.
## TSX Asynchronous Abort (TAA):
## Mitigate the vulnerability by disabling TSX.
## If TSX is enabled, clear CPU buffer rings on transitions and disable SMT.
## Currently affects Intel CPUs.
##
## https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/tsx_async_abort.html
##
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX tsx=off"
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX tsx_async_abort=full,nosmt"
## Mark all huge pages in the EPT as non-executable to mitigate iTLB multihit.
## iTLB Multihit:
## Mitigate the vulnerability by marking all huge pages in the EPT as non-executable.
## Currently affects Intel CPUs.
##
## https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/multihit.html
##
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX kvm.nx_huge_pages=force"
## Mitigations for SRBDS to prevent MDS attacks on RDRAND and RDSEED instructions
## are only possible through microcode updates from Intel.
## Special Register Buffer Data Sampling (SRBDS):
## Mitigation of the vulnerability is only possible via microcode updates from Intel.
## Currently affects Intel CPUs.
##
## https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/special-register-buffer-data-sampling.html
## https://access.redhat.com/solutions/5142691
## Enable the prctl() interface to prevent leaks from L1D on context switches.
## L1D Flushing:
## Mitigate leaks from the L1D cache on context switches by enabling the prctl() interface.
## Currently affects Intel CPUs.
##
## https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1d_flush.html
##
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX l1d_flush=on"
## Mitigate numerous MMIO Stale Data vulnerabilities and disable SMT.
## MMIO Stale Data:
## Mitigate the vulnerability by appropriately clearing the CPU buffer and disabling SMT.
## Currently affects Intel CPUs.
##
## https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/processor_mmio_stale_data.html
##
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX mmio_stale_data=full,nosmt"
## Enable mitigations for RETBleed (Arbitrary Speculative Code Execution with
## Return Instructions) vulnerability and disable SMT.
## Arbitrary Speculative Code Execution with Return Instructions (Retbleed):
## Mitigate the vulnerability through CPU-dependent implementation and disable SMT.
## Currently affects both AMD Zen 1-2 and Intel CPUs.
##
## https://en.wikipedia.org/wiki/Retbleed
## https://comsec.ethz.ch/research/microarch/retbleed/
## https://www.suse.com/support/kb/doc/?id=000020693
## https://access.redhat.com/solutions/retbleed
##
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX retbleed=auto,nosmt"
## Control RAS overflow mitigation on AMD Zen CPUs.
## Speculative Return Stack Overflow (SRSO):
## Mitigate the vulnerability by ensureing all RET instructions speculate to a controlled location.
## Currently affects AMD Zen 1-4 CPUs.
##
## https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/srso.html
##
## The default kernel setting will be utilized until provided sufficient evidence to modify.
## Using "spec_rstack_overflow=ipbp" may provide stronger security at a greater performance impact.
##
#GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX spec_rstack_overflow=safe-ret"
## Enable Gather Data Sampling (GDS) mitigation.
## Note for systems that have not received a suitable microcode update this will
## entirely disable use of the AVX instructions set.
## Gather Data Sampling (GDS):
## Mitigate the vulnerability either via microcode update or by disabling AVX.
## Note, without a suitable microcode update, this will entirely disable use of the AVX instructions set.
## Currently affects Intel CPUs.
##
## https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/gather_data_sampling.html
##
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX gather_data_sampling=force"
## Enable Register File Data Sampling (RFDS) mitigation on Intel Atom CPUs which
## encompasses E-cores on hybrid architectures.
## Register File Data Sampling (RFDS):
## Mitigate the vulnerability by appropriately clearing the CPU buffer.
## Currently affects Intel Atom CPUs (which encompasses E-cores on hybrid architectures).
##
## https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/reg-file-data-sampling.html
##