CVE-2026-97526
Received Received - Intake

Kernel Panic in Linux Kernel Due to Missing CPU Hotplug Support in PAI

Publication date: 2026-09-25

Last updated on: 2026-09-25

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: s390/pai: Support CPU hotplug for PMU PAI The command 'perf stat -e pai_crypto/CRYPTO_ALL/ -- <command>' crashes the kernel when CPUs are hotplug added during that run. Root cause is the missing allocation of per-CPU data structures for that new CPU. The allocation is dynamic and the first event that has task context creates such a structure for each online CPU. This is not sufficient. CPUs may be offline during event creation and can be set online during the perf run time. For example commands # echo 0 > /sys/devices/system/cpu/cpu1/online # perf stat -e cycles -i -- stress-ng -t10s --matrix X # sleep 1 # echo 1 > /sys/devices/system/cpu/cpu1/online Currently without a CPU hotplug handler, that new CPU has no per-CPU data infrastructure. The scheduler runs PMU call back function pai_add() to install the PMU support for that CPU before the task is being scheduled on that new CPU. In pai_add() instructions mp = this_cpu_ptr(pai_root[idx].mapptr); cpump = mp->mapptr; return a NULL pointer and the result is a kernel panic as variable cpump is used inside that function. Add CPU hotplug support for CPU add and delete and create the necessary per-CPU data infrastructure during CPU hotplug add processing. Same for CPU hotplug remove. This is done when the CPU is offline to ensure the data structures are available when CPU is made online and tasks are scheduled on it. [hca@linux.ibm.com: fixup error path in pai_init()]

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Meta Information

Published
2026-09-25
Last Modified
2026-09-25
Generated
2026-10-15
AI Q&A
2026-09-25
EPSS Evaluated
2026-10-14
NVD
CVE-2026-97526
EUVD
EUVD-2026-86834

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

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel affects the s390/pai component, specifically related to CPU hotplug functionality for the PMU PAI feature. The issue occurs when using the 'perf stat' command with CPU hotplug operations. If a CPU is brought online during a perf run, the kernel crashes because per-CPU data structures are not properly allocated for the new CPU. This happens because the allocation only occurs when an event with task context is created, which may not account for CPUs that are offline during event setup but brought online later.

Detection Guidance

The vulnerability can be detected by checking if the perf stat command with pai_crypto events crashes the kernel during CPU hotplug operations. Monitor for kernel panics when CPUs are brought online during perf stat execution.

Impact Analysis

This vulnerability can cause a kernel panic, leading to system crashes and potential data loss or service disruption. If you are using the 'perf stat' command with CPU hotplug operations on a s390 system with PMU PAI enabled, the system may crash when CPUs are dynamically added or removed during perf monitoring sessions.

Compliance Impact

This vulnerability causes kernel panics when CPUs are hotplugged during perf stat commands, leading to system crashes. Such instability could disrupt data processing operations, potentially violating availability requirements in GDPR and HIPAA.

Mitigation Strategies

Apply the Linux kernel patch that adds CPU hotplug support for PMU PAI. Ensure per-CPU data structures are allocated during CPU hotplug operations to prevent kernel panics when CPUs are brought online during perf events.

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