CVE-2026-97526

Status: UPDATED  |  Advisory ID: CVE-2026-97526

Key Details

Affected Products, Subsystems & Sectors

What to Know

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()] (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References