Executive brief
A vulnerability in the Linux kernel for PowerPC systems can cause the entire operating system to crash (kernel panic) when the hardware encounters certain error conditions known as machine check exceptions. This occurs because the system incorrectly attempts to manage task scheduling while in a restricted hardware state, leading to an immediate system failure. This issue primarily impacts system availability and could lead to data loss if the system crashes during critical operations.
Technical details
A vulnerability in the PowerPC architecture's time management code within the Linux kernel leads to a kernel panic during Machine Check Exception (MCE) handling. The function `arch_irq_work_raise()` incorrectly calls `preempt_disable()` while the processor is running in 'real mode' (NMI context). In this restricted execution environment, accessing the `preempt_count` can trigger a data access fault, resulting in a recursive exception or immediate 'Oops'. The fix involves removing the redundant preemption calls, as the context (NMI with interrupts disabled) already guarantees that the code cannot be preempted. This issue affects PowerPC systems and is triggered by hardware-level machine checks.
Affected products
- Linux Linux Kernel powerpc architecture
Timeline
- 2026-05-13: patched: Initial fix authored by Sayali Patil
- 2026-07-24: advisory: NVD publication date
References
- https://git.kernel.org/stable/c/31467b23823ffec1f6fff407f8e3ca9af8b7491a
- https://git.kernel.org/stable/c/51860e423592893cd7bfa7287d99a3aff4dc3a9d
- https://git.kernel.org/stable/c/6dcd072a5ae3aed336e4a67a7d4cc5205b240065
- https://git.kernel.org/stable/c/72d8d1c36452a4d3ee134b1da48de7518c1329f9
- https://git.kernel.org/stable/c/8079acc5ee5235a627e4586d4f42082a9000ea64
- https://git.kernel.org/stable/c/a09d07ac45e283c9861a9ceea06f56d0ba851d22