CVE-2026-97526

/// Technical 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

/// 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