diff --git a/README.md b/README.md index f784bbf4..5e06af6a 100644 --- a/README.md +++ b/README.md @@ -141,6 +141,11 @@ Mitigations for known CPU vulnerabilities are enabled in their strictest form and simultaneous multithreading (SMT) is disabled. See the `/etc/default/grub.d/40_cpu_mitigations.cfg` configuration file. +Importantly, we do not rely on the use of the already enabled-by-default `mitigations=auto` +kernel boot parameter to perform CPU mitigations like many other distributions. This is +because it's use is both totally redundant and it does not apply all hardening settings +to their strictest possible levels. See issue: https://github.com/Kicksecure/security-misc/issues/199#issuecomment-3327391859. + Note, to achieve complete protection for known CPU vulnerabilities, the latest security microcode (BIOS/UEFI) updates must be installed on the system. Furthermore, if using Secure Boot, the Secure Boot Forbidden Signature Database (DBX) must be kept diff --git a/etc/default/grub.d/40_cpu_mitigations.cfg#security-misc-shared b/etc/default/grub.d/40_cpu_mitigations.cfg#security-misc-shared index 8f18ad06..ce0e112f 100644 --- a/etc/default/grub.d/40_cpu_mitigations.cfg#security-misc-shared +++ b/etc/default/grub.d/40_cpu_mitigations.cfg#security-misc-shared @@ -34,11 +34,21 @@ ## https://uefi.org/revocationlistfile ## https://github.com/fwupd/fwupd -## Enable a subset of known mitigations for some CPU vulnerabilities and disable SMT. +## Enable a subset of known default mitigations for some CPU vulnerabilities and disable SMT. +## Note that this redundant parameter simply applies each mitigation at the already applied default settings. +## The default values are not always the strictest and so we reapply each below to their highest setting. +## We retain it here for completeness as many other distributions heavily rely on this for many CPU mitigations. +## +## https://github.com/Kicksecure/security-misc/issues/199#issuecomment-3327391859 +## https://github.com/secureblue/secureblue/issues/1405 +## https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/attack_vector_controls.html ## ## KSPP=yes ## KSPP sets the kernel parameters. ## +## WARNING: Do not rely on this parameter, it is presented here only for educational purposes. +## WARNING: Parameters are applied consecutively and so do not ever move this setting down. +## GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX mitigations=auto,nosmt" ## Disable SMT as it has been the cause of and amplified numerous CPU exploits.