Linux Kernel EUVD-2026-32478

The Linux kernel's md (Multiple Devices) subsystem provides software RAID functionality. Within it, llbitmap implements a lazy/write-intent bitmap used to track which regions of a RAID array are synchronized - critical for crash recovery and resync operations. llbitmap_start_write() and llbitmap_start_discard() are entry points for initiating write and discard operations on the RAID. Both functions call llbitmap_state_machine() to manage transitions between bitmap states, but the barrier - which serializes access to prevent concurrent modification - was being raised after the state machine was already invoked. This ordering error is a classic TOCTOU-adjacent race: if another thread or interrupt triggers a competing state transition in the gap before the barrier is raised, the bitmap state can become inconsistent, leading to kernel panic or md array failure. The CPE (cpe:2.3:o:linux:linux_kernel:*) confirms this affects the Linux kernel broadly, with the affected commit range starting from 5ab829f1971dc99f2aac10846c878e67fc875abc. No CWE was assigned, but the root cause class is CWE-362 (Concurrent Execution Using Shared Resource with Improper Synchronization).