CVE-2026-80626
Received Received - Intake

PowerPC perf preempt count underflow in Linux kernel

Publication date: 2026-08-28

Last updated on: 2026-08-28

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: powerpc/perf: fix preempt count underflow in fsl_emb_pmu_del fsl_emb_pmu_del() unconditionally calls put_cpu_var(cpu_hw_events) at the 'out:' label, but only calls the matching get_cpu_var() after the 'i < 0' early-return check. When event->hw.idx is negative the function jumps to 'out:' without having taken get_cpu_var(), and the trailing put_cpu_var() then issues an unmatched preempt_enable(), underflowing preempt_count. On a CONFIG_PREEMPT=y kernel preempt_count would underflow and eventually present as a 'scheduling while atomic' BUG. Move put_cpu_var() to pair with get_cpu_var() so the percpu access is correctly bracketed and the 'out:' label only handles perf_pmu_enable.

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Meta Information

Published
2026-08-28
Last Modified
2026-08-28
Generated
2026-09-17
AI Q&A
2026-08-28
EPSS Evaluated
2026-09-15
NVD
CVE-2026-80626
EUVD
EUVD-2026-67502

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 is a Linux kernel vulnerability where a function called fsl_emb_pmu_del() incorrectly handles CPU variable access. It calls put_cpu_var() without a matching get_cpu_var() when an early return condition is met, causing a preempt count underflow. This can lead to a 'scheduling while atomic' bug in kernels with CONFIG_PREEMPT enabled.

Detection Guidance

This vulnerability is specific to the Linux kernel's powerpc/perf subsystem and may trigger a 'scheduling while atomic' BUG on CONFIG_PREEMPT=y kernels. Detection requires checking kernel logs for this BUG message or verifying the affected function fsl_emb_pmu_del() behavior.

Impact Analysis

If you run a Linux system with a preemptible kernel (CONFIG_PREEMPT=y), this bug could cause system instability or crashes. It may manifest as kernel errors or unexpected system hangs during performance monitoring operations.

Compliance Impact

This vulnerability does not directly affect compliance with standards like GDPR or HIPAA as it is a low-level kernel issue related to preempt count underflow in the Linux kernel's powerpc performance monitoring unit. It may indirectly impact compliance if the affected system is used in environments requiring strict uptime or reliability, but no direct regulatory impact is specified.

Mitigation Strategies

Apply the Linux kernel patch that resolves this issue by moving put_cpu_var() to pair with get_cpu_var() in fsl_emb_pmu_del(). Alternatively, disable CONFIG_PREEMPT if possible, but this may impact system performance.

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