CVE-2026-64214
Received Received - Intake

Kernel Panic in Linux Kernel Due to Machine Check Exception Handling

Publication date: 2026-07-24

Last updated on: 2026-07-24

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: powerpc/time: Remove redundant preempt_disable|enable() calls from arch_irq_work_raise() A kernel panic is observed when handling machine check exceptions from real mode. BUG: Unable to handle kernel data access on read at 0xc00000006be21300 Oops: Kernel access of bad area, sig: 11 [#1] MSR: 8000000000001003 <SF,ME,RI,LE> CR: 88222248 XER: 00000005 CFAR: c00000000003ffc4 DAR: c00000006be21300 DSISR: 40000000 IRQMASK: 0 NIP [c000000000029e40] arch_irq_work_raise+0x10/0x70 LR [c00000000003ffc8] machine_check_queue_event+0xa8/0x150 Call Trace: [c0000000179d3c70] [c00000000003ff64] machine_check_queue_event+0x44/0x150 [c0000000179d3d30] [c0000000000084e0] machine_check_early_common+0x1f0/0x2c0 The crash occurs because arch_irq_work_raise() calls preempt_disable() from machine check exception (MCE) handlers running in real mode. In this context, accessing the preempt_count can fault, leading to the panic. The preempt_disable()/preempt_enable() pair in arch_irq_work_raise() was originally added by commit 0fe1ac48bef0 ("powerpc/perf_event: Fix oops due to perf_event_do_pending call") to avoid races while raising irq work from exception context. Later, commit 471ba0e686cb ("irq_work: Do not raise an IPI when queueing work on the local CPU") added preemption protection in irq_work_queue() path, while commit 20b876918c06 ("irq_work: Use per cpu atomics instead of regular atomics") added equivalent protection in irq_work_queue_on() before reaching arch_irq_work_raise(): irq_work_queue() / irq_work_queue_on() -> preempt_disable() -> __irq_work_queue_local() -> irq_work_raise() -> arch_irq_work_raise() As a result, callers other than mce_irq_work_raise() already execute with preemption disabled, making the additional preempt_disable()/preempt_enable() pair in arch_irq_work_raise() redundant. The arch_irq_work_raise() function executes in NMI context when called from MCE handler. Hence we will not be preempted or scheduled out since we are in NMI context with MSR[EE]=0. Therefore, it is safe to remove the preempt_disable()/preempt_enable() calls from here. Remove it to avoid accessing preempt_count from real mode context. [Maddy: Fixed the commit title]

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Meta Information

Published
2026-07-24
Last Modified
2026-07-24
Generated
2026-07-24
AI Q&A
2026-07-24
EPSS Evaluated
N/A
NVD
CVE-2026-64214
EUVD
EUVD-2026-48622

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves redundant preempt_disable() and preempt_enable() calls in the arch_irq_work_raise() function. When handling machine check exceptions from real mode, these calls can cause a kernel panic because accessing preempt_count faults in this context. The issue arises as the function runs in NMI context with preemption already disabled, making the extra calls unnecessary and unsafe.

Detection Guidance

This vulnerability is specific to the Linux kernel and manifests as a kernel panic during machine check exceptions. Detection requires checking kernel logs for oops messages or kernel panics related to arch_irq_work_raise or machine check exceptions.

Impact Analysis

This vulnerability can cause system crashes (kernel panics) when machine check exceptions occur. Affected systems may become unresponsive or reboot unexpectedly, leading to potential data loss or service disruption. It primarily impacts PowerPC-based Linux systems running in real mode during exception handling.

Compliance Impact

This vulnerability does not directly affect compliance with GDPR, HIPAA, or similar standards as it is a Linux kernel issue causing kernel panics during machine check exceptions. Compliance impacts would only occur if the kernel panic disrupts data processing or security controls, which is not specified in the provided context.

Mitigation Strategies

Apply the kernel patch that removes the redundant preempt_disable/enable calls from arch_irq_work_raise. Update to a fixed kernel version where this issue is resolved.

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