The Linux Kernel versions 4.14, 4.15, and 4.16 has a null pointer dereference which can result in an out of memory (OOM) killing of large mlocked processes. The issue arises from an oom killed process's final thread calling exit_mmap(), which calls munlock_vma_pages_all() for mlocked vmas.This can happen synchronously with the oom reaper's unmap_page_range() since the vma's VM_LOCKED bit is cleared before munlocking (to determine if any other vmas share the memory and are mlocked).
https://usn.ubuntu.com/3752-3/
https://usn.ubuntu.com/3752-2/
https://usn.ubuntu.com/3752-1/
https://marc.info/?l=linux-kernel&m=152460926619256
https://marc.info/?l=linux-kernel&m=152400522806945
https://access.redhat.com/security/cve/cve-2018-1000200
https://access.redhat.com/errata/RHSA-2018:2948