Dm-X: Protecting Volume-Level Integrity For Cloud Volumes And Local Block Devices

The verified boot feature in recent Android devices, which deploys dm-verity, has been overwhelmingly successful in eliminating the extremely popular Android smart phone rooting movement [25]. Unfortunately, dm-verity integrity guarantees are read-only and do not extend to writable volumes.This paper introduces a new device mapper, dm-x, that efficiently (fast) and reliably (metadata journaling) assures volume-level integrity for entire, writable volumes. In a direct disk setup, dm-x overheads are around 6-35% over ext4 on the raw volume while offering additional integrity guarantees. For cloud storage (Amazon EBS), dm-x overheads are negligible.