CVE-2026-80611

A flaw was found in the Linux kernel's Advanced Configuration and Power Interface (ACPI) processor idle functionality. When kernel tracing features, such as function tracing or Kprobes, are enabled, entering a Low Power Idle (LPI) state can trigger a Read-Copy Update (RCU) warning. This occurs because the system attempts to record trace data after RCU has been disabled for the current CPU, leading to diagnostic errors. The primary consequence is system instability or unexpected behavior related to kernel tracing mechanisms.

A flaw of low impact was found in the Linux kernel's ACPI processor idle handling as shipped in Red Hat Enterprise Linux and Red Hat In-Vehicle OS. When kernel tracing features such as function tracing (ftrace) or Kprobes are enabled, entering an ACPI Low Power Idle (LPI) state can trigger a Read-Copy-Update (RCU) warning: the acpi_idle_lpi_enter() function runs in the cpuidle path after RCU has already been disabled for the local CPU, while ftrace's function_trace_call() expects RCU to be actively watching before recording trace data. The primary consequence is an RCU splat, warning output, and possible system instability or unexpected behavior limited to the tracing path; there is no evidence of memory corruption, information disclosure, or privilege escalation, and triggering requires local access with the privileges needed to enable kernel tracing. For this reason Red Hat rates the impact of this flaw as low despite the CVSS 3.1 base score of 5.5. The kernel and kernel-rt packages in Red Hat Enterprise Linux 8, 9, and 10, and the Red Hat In-Vehicle OS 2 kernels, are affected; given the low impact and diagnostic nature of the issue, the fix is currently deferred for these streams, leaving a residual risk of trace-induced RCU warnings and log noise during idle entry on systems running with tracing enabled. Red Hat Enterprise Linux 7 kernels are not affected because the vulnerable code is not present, and Red Hat Enterprise Linux 6 ELS is out of support scope.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

This issue only manifests when kernel function tracing (ftrace) or Kprobes are enabled, which is not the default configuration. Disabling or avoiding function tracing and Kprobe instrumentation on affected systems prevents the RCU warnings from being triggered during ACPI Low Power Idle entry.