Executive brief
A vulnerability was identified in the Linux kernel's task monitoring system, which is responsible for detecting and reporting processes that have stopped responding. On certain hardware architectures, this component could trigger system warnings or instability due to how it tracks internal locks. While primarily affecting system reliability and diagnostics, it could potentially be leveraged to impact system availability.
Technical details
The vulnerability exists within the hung_task blocker tracking mechanism, which assumes lock pointers are at least 4-byte aligned to use the lower bits for type encoding. On architectures such as m68k that only guarantee 2-byte alignment, this assumption is violated, triggering WARN_ON_ONCE checks. An attacker could potentially exploit this to cause a denial of service or system instability by triggering these kernel warnings repeatedly. The fix involves adjusting runtime checks to silently ignore locks that do not meet the 4-byte alignment requirement, effectively disabling the tracking feature for those specific instances. Patches have been merged into the stable Linux kernel tree.
Affected products
- Linux Linux Kernel 6.16 to 6.17.6
Timeline
- 2025-12-16: disclosed
- 2025-10-29: patched