CVE-2026-99017

In the Linux kernel, the following vulnerability has been resolved:

riscv: errata: select RISCV ALTERNATIVE EARLY for THEAD GHOSTWRITE

errata probe ghostwrite() only marks the CPU as vulnerable when it is called at the RISCV ALTERNATIVES EARLY BOOT stage, and the mitigation in ghostwrite enable mitigation() only takes effect if the vulnerable state was recorded before the boot alternatives are patched.

The early boot stage is only executed when CONFIG RISCV ALTERNATIVE EARLY is enabled, which currently is only selected by ERRATA THEAD MAE. In a kernel built with ERRATA THEAD GHOSTWRITE=y but ERRATA THEAD MAE=n, the early alternatives never run, so ghostwrite state is never set to VULNERABLE: ghostwrite enable mitigation() returns false, xtheadvector remains enabled, and sysfs reports "Not affected" on a vulnerable T-Head C9xx CPU.

Select RISCV ALTERNATIVE EARLY from ERRATA THEAD GHOSTWRITE so that the vulnerability is detected in the early boot stage and the default mitigation is applied.