Linux Kernel CPU Hotplug Removal Vulnerability in s390 Products

CVE-2024-57849

Summary

A vulnerability exists in the Linux kernel's handling of CPU hotplug operations within the s390 architecture. Specifically, when a CPU is hot-plugged off, the associated performance monitoring unit (PMU) deallocates sampling data buffers. However, if an event remains active on the removed CPU, the kernel's performance subsystem attempts to retrieve samples from buffers that may already have been freed. This could lead to a use-after-free scenario, potentially exposing invalid data. To mitigate this, there needs to be a check to ascertain whether the CPU remains in a reserved state. If the PMU_F_RESERVED bit is set, it indicates that the buffers are still valid; otherwise, they may be lost. Prompt application of the provided fixes is essential to ensure system integrity and performance.

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