Affected: Linux

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.