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()]
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()]
Published:
2026-09-25
Score:
n/a
EPSS:
n/a
KEV:
No
Analysis and contextual insights are available on OpenCVE Cloud.
Remediation
No vendor fix or workaround currently provided.
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Tracking
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Advisories
No advisories yet.
References
History
Fri, 25 Sep 2026 10:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| 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()] | |
| Title | s390/pai: Support CPU hotplug for PMU PAI | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-09-25T10:21:28.923Z
Reserved: 2026-09-24T16:01:01.152Z
Link: CVE-2026-97526
No data.
Status : Received
Published: 2026-09-25T11:17:02.767
Modified: 2026-09-25T11:17:02.767
Link: CVE-2026-97526
No data.
OpenCVE Enrichment
Updated: 2026-09-25T16:30:15Z
Weaknesses
No weakness.