CVE-2026-68166
Description
AI Translation Available
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 UFFDIO_COPY.
Update vma_can_userfault() to reject VM_SHADOW_STACK.
While on it, also reject VM_SPECIAL so that if a driver would implement
vm_uffd_ops, it wouldn't be possible to register special VMAs with
userfaultfd.
Since VM_SPECIAL includes VM_DONTEXPAND which is set but hugetlb, exclude
hugetlb VMAs from the check for VM_SPECIAL.
https://git.kernel.org/stable/c/0c26202b157f1efc3cd2f26f5c30f59b508a6a5d
https://git.kernel.org/stable/c/165613191ad9d034bf17c00e3a142f9561597ec5
https://git.kernel.org/stable/c/3c58f641e813c3c71039f8fd4d4e2a3aab713288