UBUNTU-CVE-2026-80611: Low severity ubuntu/linux-azure vulnerability
In the Linux kernel, the following vulnerability has been resolved: ACPI: processoridle: 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: acpiidlelpienter+0x4/0xd8 WARNING: CPU: 8 PID: 0 at include/linux/tracerecursion.h:162 functiontracecall+0x1e8/0x228 The acpiidlelpienter() function is invoked within the cpuidle path after RCU has already been disabled for the current local CPU. Consequently, ftrace's functiontracecall() expects RCU to be actively watching before recording trace data, emitting a warning if it is not. Fix this by annotating acpiidlelpienter(), the generic weak stub, and the RISC-V implementation of acpiprocessorffhlpienter() 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 warnings during idle entry.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 6.8.0-147.147 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 6.8.0-1067.70 - Upgrade
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ubuntu/linux-aws-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1014.14~24.04.1 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79 - Upgrade
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ubuntu/linux-azure-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1017.17~24.04.1 - Upgrade
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ubuntu/linux-azure-fdeto a version that resolves this vulnerability.Fixed in 6.8.0-1069.76 - Upgrade
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ubuntu/linux-azure-fde-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1016.16~24.04.1 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79 - Upgrade
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ubuntu/linux-gcp-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1014.14~24.04.1 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 6.8.0-1066.74 - Upgrade
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ubuntu/linux-gkeopto a version that resolves this vulnerability.Fixed in 6.8.0-1052.56 - Upgrade
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ubuntu/linux-hwe-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-38.38~24.04.4 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 6.8.0-1067.68 - Upgrade
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ubuntu/linux-lowlatencyto a version that resolves this vulnerability.Fixed in 6.8.0-147.147.1 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 6.8.0-1064.67 - Upgrade
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ubuntu/linux-oracle-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1013.13~24.04.1 - Upgrade
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ubuntu/linux-riscv-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-38.38.1~24.04.1 - Upgrade
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ubuntu/linux-bluefieldto a version that resolves this vulnerability.Fixed in 6.8.0-1033.38 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 6.8.1-1062.63 - Upgrade
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ubuntu/linux-aws-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1067.70+fips1 - Upgrade
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ubuntu/linux-azure-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79+fips1 - Upgrade
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ubuntu/linux-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-147.147+fips1 - Upgrade
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ubuntu/linux-gcp-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79+fips1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-38.38 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1014.14 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
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ubuntu/linux-azure-fdeto a version that resolves this vulnerability.Fixed in 7.0.0-1016.16 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.0.0-1014.14 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 7.0.0-1008.9 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 7.0.0-1015.15 - Upgrade
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ubuntu/linux-oem-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1015.15 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 7.0.0-1013.13 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 7.0.0-38.38.1 - Upgrade
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-38.38.1 - Compensating control
Annotate acpi_idle_lpi_enter(), the generic __weak stub, and the RISC-V implementation of acpi_processor_ffh_lpi_enter() with __cpuidle, moving them into the .cpuidle.text section and implicitly disabling ftrace instrumentation on this path.
Event History
Frequently Asked Questions
When can this issue occur?
It can occur when a system enters an ACPI Low Power Idle state while function tracing or Kprobes is enabled. Under those conditions, tracing instrumentation can emit an RCU warning during idle entry.
Are systems using the default kernel configuration necessarily affected?
The described warning depends on function tracing or Kprobes being enabled. The data does not indicate that the warning occurs when those tracing mechanisms are not enabled.
What is the practical impact?
The reported impact is an RCU warning caused by ftrace attempting to record trace data after RCU has been disabled on the local CPU during the cpuidle path. The provided information does not describe privilege escalation, data exposure, or code execution.
How can I identify whether a system is encountering the issue?
Check kernel logs for an RCU warning naming acpi_idle_lpi_enter, such as "RCU not on for: acpi_idle_lpi_enter," with a stack trace involving function_trace_call. This is most relevant on systems using ACPI LPI idle states with function tracing or Kprobes enabled.
What mitigation is available if an updated kernel cannot be deployed immediately?
Avoid enabling function tracing or Kprobes on affected systems where possible. The issue is triggered by trace instrumentation during entry into an ACPI Low Power Idle state.