Linux Kernel Vulnerability Impacting RCU State Management

CVE-2022-49709

Summary

A vulnerability in the Linux kernel's management of Read-Copy-Update (RCU) state can lead to an invalid RCU state in the cpuidle code path. Specifically, improper handling during the __cfi_slowpath_diag function can cause warnings and potential instability. The issue arises from using RCU_NONIDLE in an inappropriate context, leading to unsafe kernel behavior and impacting system performance. The correct approach involves utilizing rcu_irq_enter/exit to manage RCU wake-ups efficiently while properly disabling interrupts during shadow/module checks.

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