CVE-2026-99125

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

s390/pai: Handle multiple PMU stop callback invocations

Handle the following scenario: The kernel protects itself against a very high sampling load and throttles the sampling using:

perf event throttle() --> PMU->stop()

Shortly later the scheduler may terminate the task and removes it from the CPU. It again calls

PMU->stop()

which results in two invocations of PMU->stop() called back to back. Protect against this and check the PERF HES STOPPED bit on function entry. If it is already set return. Clear bit PERF HES STOPPED in PMU->start().

Prohibit ioctl(fd, PERF EVENT IOC PERIOD, ...) call for this event. It sets perf event::event limit to a positive value and causes perf event overflow() to invoke pai stop() call back function when perf event::event limit hits zero. This is not supported because the sample events CRYPTO ALL and NNPA ALL are only taken at schedule out of a task.

Use list for each entry safe() for safe iteration over syswide list in pai have samples().