Executive Summary

This vulnerability exists in the Linux kernel's perf subsystem, specifically in the AMD IBS (Instruction Based Sampling) component. The issue arises because the function perf_allow_kernel() is called from within the NMI (Non-Maskable Interrupt) handler context, which is unsafe and could potentially cause fatal errors.

The fix involves capturing the permission at the event initialization time by storing it in a cached flag (event->hw.flags), so that the NMI handler can rely on this cached flag instead of calling perf_allow_kernel() directly during the NMI context.

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Impact Analysis

Because calling perf_allow_kernel() from the NMI context is unsafe, this vulnerability could lead to fatal errors or crashes in the Linux kernel when the perf subsystem is used with AMD IBS. This could result in system instability or unexpected kernel panics.

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