CVE-2026-68166

Summary

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.

Affected Software

VendorProductVersion RangeStatus
LinuxLinux54007f818206dc27309ca423df4c87dd160a7208 < 165613191ad9d034bf17c00e3a142f9561597ec5affected
LinuxLinux54007f818206dc27309ca423df4c87dd160a7208 < 0c26202b157f1efc3cd2f26f5c30f59b508a6a5daffected
LinuxLinux54007f818206dc27309ca423df4c87dd160a7208 < 3c58f641e813c3c71039f8fd4d4e2a3aab713288affected
LinuxLinux6.6affected
LinuxLinux0 < 6.6unaffected
LinuxLinux6.18.44 <= 6.18.*unaffected
LinuxLinux7.1.6 <= 7.1.*unaffected
LinuxLinux7.2-rc5 <= *unaffected

Weaknesses

References