CVE-2026-31787 xen/privcmd: fix double free via VMA splitting

In the Linux kernel, the following vulnerability has been resolved: xen/privcmd: fix double free via VMA splitting privcmdvmops defines .close privcmdclose, but neither .maysplit nor .open. When userspace does a partial munmap on a privcmd mapping, the kernel splits the VMA via splitvma. Since...