| Description: | 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). It was discovered that, when attempting to handle an out-of-memory situation, a null pointer dereference could be triggered in the Linux kernel in some circumstances. A local attacker could use this to cause a denial of service (system crash).
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