In the Linux kernel, the following vulnerability has been resolved: userfaultfd: prevent registration of special VMAs Vova Tokarev says: userfaultfd allows registration on shadow stack VMAs. With userfaultfd access, you can register on the shadow stack, discard a page ... and inject a page with chosen return addresses via UFFDIOCOPY. Update vmacanuserfault() to reject VMSHADOWSTACK. While on it, also reject VMSPECIAL so that if a driver would implement vmuffdops, it wouldn't be possible to register special VMAs with userfaultfd. Since VMSPECIAL includes VMDONTEXPAND which is set but hugetlb, exclude hugetlb VMAs from the check for VM_SPECIAL.