CVE-2026-80611

/// Technical description

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

ACPI: processor_idle: Mark LPI enter functions as __cpuidle

When function tracing or Kprobes is enabled, entering an ACPI Low

Power Idle (LPI) state triggers the following RCU splat:

RCU not on for: acpi_idle_lpi_enter+0x4/0xd8

WARNING: CPU: 8 PID: 0 at include/linux/trace_recursion.h:162 function_trace_call+0x1e8/0x228

The acpi_idle_lpi_enter() function is invoked within the cpuidle

path after RCU has already been disabled for the current local CPU.

Consequently, ftrace's function_trace_call() expects RCU to be

actively watching before recording trace data, emitting a warning

if it is not.

Fix this by annotating acpi_idle_lpi_enter(), the generic __weak

stub, and the RISC-V implementation of acpi_processor_ffh_lpi_enter()

with __cpuidle. This moves these functions into the '.cpuidle.text'

section, implicitly disabling ftrace instrumentation (notrace) along

this sensitive path and preventing trace-induced RCU

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References