perf/x86/intel/uncore Array Overflow in Linux Kernel

Executive Summary

This vulnerability exists in the Linux kernel's perf subsystem for Intel uncore performance monitoring. Specifically, when NUMA is disabled and the system boots with fewer CPUs than expected in die 0, the discovery table for offline dies is still parsed.

Because the discovery table continues to be parsed even if all CPUs in a die are offline, it can lead to an array overflow at the code location pmu->boxes[die] = box in the function uncore_pci_pmu_register().

This overflow can trigger warnings or potentially cause other issues related to system stability or security.

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Impact Analysis

The vulnerability can cause an array overflow in the Linux kernel's performance monitoring code, which may trigger system warnings or lead to other unspecified issues.

Such an overflow could potentially affect system stability or reliability, possibly causing crashes or unexpected behavior.

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Detection Guidance

This vulnerability can be detected by observing specific kernel warning messages related to the intel_uncore module. In particular, the warning message "WARNING: CPU: <number> PID: <number> at uncore.c:1157 uncore_pci_pmu_register+0x136/0x160 [intel_uncore]" indicates the issue.

To detect this on your system, you can check the kernel logs for such warnings using commands like:

• dmesg | grep -i 'uncore_pci_pmu_register'
• journalctl -k | grep -i 'uncore_pci_pmu_register'
• grep -i 'uncore_pci_pmu_register' /var/log/kern.log

These commands search for the warning message in kernel logs, which can help identify if the vulnerability is present due to the array overflow condition triggered when CPUs in a die are offline.

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