A proposed Linux kernel patch would provide a new Kconfig build time option of "CONFIG_DEFAULT_CPU_MITIGATIONS_OFF" to build an insecure kernel if wanting to avoid the growing list of CPU security mitigations within the kernel and their associated performance overhead. . While risking system security, booting the Linux kernel with the " mitigations=off " option has been popular for avoiding the performance costs of Spectre, Meltdown, and the many other CPU security vulnerabilities that have come to light in recent years. Using mitigations=off allows run-time disabling of the various in-kernel security mitigations for these CPU problems. A patch proposed this week would provide CONFIG_DEFAULT_CPU_MITIGATIONS_OFF as a Kconfig switch that could optionally be enabled to have the same affect as mitigations=off but to be applied at build-time to avoid having to worry about setting the "mitigations=off" flag. The link for this article located at Phoronix is no longer available. . Turning off CPU security features during the build process through a new Kconfig option may enhance performance but poses potential security threats.. Linux Kernel Patch, CPU Mitigations, Performance Enhancements, Security Risks. . Brittany Day
Made public earlier this year was Spectre-BHB / BHI as a speculative execution vulnerability similar to Spectre V2 and affecting Intel and Arm CPUs. . At the time Neoverse N2 / N1 / V1 and older cores like Cortex-A15 / A57 / A72 were known to be vulnerable and required software mitigations. The upcoming AmpereOne is also vulnerable to Spectre-BHB and has a patch now on its way to the Linux kernel for mitigating this Spectre class vulnerability. Spectre-BHB targets the CPU's Branch History Buffer and affects a wide range of Arm cores. Arm's documentation around Spectre-BHB can be found via developer.arm.com . The link for this article located at Phoronix is no longer available. . The recent update from AmpereOne addressing Spectre-BHB outlines essential measures for safeguarding CPU integrity in Linux systems.. AmpereOne, Spectre-BHB, Linux Kernel Mitigation, Arm CPU Security. . Brittany Day
Following the July disclosure of the Retbleed CPU security vulnerability affecting older processors and an AMD change made in August, here is a fresh look at the performance impact of the Retbleed mitigations on Linux, including if opting for the IBPB-based Retbleed mitigation, and the accumulated CPU security mitigation impact for Zen 2 with the flagship Ryzen 9 3950X processor. . Being curious about the Retbleed performance impact for the Ryzen 9 3950X following my earlier Zen 1 testing as well as Intel Skylake testing, I ran some benchmarks looking at the AMD Ryzen 9 3950X in different mitigation states with the latest kernel code. As a reminder, Retbleed on the AMD side affects only Zen 2 CPUs and older -- not current generation Zen 3 or the upcoming Zen 4 processors. The link for this article located at Phoronix is no longer available. . Retbleed is a vulnerability in modern processors such as AMD Ryzen, allowing possible information leakage. AMD's patches, however, may sacrifice performance for enhanced security. Retbleed Mitigation,Ryzen 9 3950X Performance,AMD CPU Security,Zen 2 Mitigation Effects,CPU Threat Evaluations. . LinuxSecurity.com Team
Get the latest Linux and open source security news straight to your inbox.