CVE-2026-89460

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

s390/cpum_cf: Handle CPU hotplug via prepare/dead callbacks

The command 'perf stat -e cycles -- <command>' crashes the kernel

when CPUs are hotplug added during that run.

Root cause is the allocation of struct cpu_cf_events at first

event initialization. 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

create an event for CPUs 0,2-X. Since the events are created with

task-context, the scheduler will eventually schedule the program

on CPU1. This CPU has not created and initialized any per

CPU event infrastructure as that CPU was not online at the time

of the

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References