Executive brief
A vulnerability in the Linux kernel's debug tracking system could cause a system deadlock during the early stages of the computer's boot process. This issue specifically affects systems running real-time (PREEMPT_RT) configurations on ARM64 hardware. If triggered, the system may hang or crash before it fully starts, leading to a complete denial of service.
Technical details
A deadlock condition exists in lib/debugobjects.c when booting a PREEMPT_RT kernel on ARM64. During early boot, interrupts are enabled before the scheduler is initialized (SYSTEM_SCHEDULING state). If a hard interrupt fires during this window and attempts to call fill_pool(), it may hit a code region already holding a lock required for the allocation path, resulting in a lock inversion or deadlock. The fix introduces a can_fill_pool() helper to explicitly exclude allocations from hard interrupt context during this early boot phase. Patches have been applied to multiple stable branches including 6.19.y and 7.x.
Affected products
- Linux Linux 6.19, 7.0.13, 7.1
Timeline
- 2026-06-05: other: Initial patch authored
- 2026-07-01: disclosed: CVE published