Executive brief
A vulnerability in the Linux kernel's handling of AMD Zen2 processors could allow for improper isolation of shared resources within the processor's operation cache. This flaw could lead to instruction corruption, potentially causing system instability or unpredictable behavior on affected hardware. The issue has been addressed by implementing a configuration fix in the kernel's CPU initialization code.
Technical details
A vulnerability was identified in the Linux kernel's x86 CPU initialization for AMD Zen2 architecture. The flaw stems from improper isolation of shared resources within the 'op cache' (operation cache), which can result in instruction corruption. The fix involves setting a specific bug fix bit (bit 33) in the MSR_ZEN4_BP_CFG Model Specific Register (0xc001102e) during the initialization of Zen2 cores, provided the system is not running under a hypervisor. This ensures that hardware resources are correctly partitioned to prevent cross-context instruction interference. Patch sets have been backported to multiple stable kernel branches.
Affected products
- Linux Linux Kernel Zen2 architecture CPUs
Timeline
- 2025-12-09: other: Initial patch authored by AMD engineers
- 2026-05-14: patched: Patches committed to stable kernel trees
- 2026-05-28: disclosed: CVE published and NVD record created
References
- https://git.kernel.org/stable/c/1cd85a19748b2407830376a5cbae5c0f126016e5
- https://git.kernel.org/stable/c/1e23b30a80b14e5764657401ee2cca030525ae8e
- https://git.kernel.org/stable/c/251497955f2314cd39d43191e81c6151dead4c7b
- https://git.kernel.org/stable/c/28f5ed477eef166d678d6966762cbc1de9b4f436
- https://git.kernel.org/stable/c/9109489cc8c34e50d15575a3d1ff82af586bc1aa
- https://git.kernel.org/stable/c/c21b90f77687075115d989e53a8ec5e2bb427ab1
- https://git.kernel.org/stable/c/f5bc3aef7df46eaaf423d7413ab8833f704ae576