CVE-2026-99168

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

mshv vtl: Check per-CPU register page before mmap

Register-page setup is optional for each CPU. If allocation or registration fails, mshv vtl configure reg page() warns and leaves that CPU's reg page NULL, but initial context setup continues successfully. Meanwhile, successful setup on another CPU sets the global mshv has reg page flag.

mshv vtl fault() checks this global flag before selecting the requested CPU's register page. With mixed setup results across online CPUs, the check passes even for a CPU with no register page, reaching get page(NULL) when userspace faults in that mapping.

Check the selected per-CPU register page before taking its reference and return VM FAULT SIGBUS if it is absent.