CVE-2022-49709 in Linux
Summary
by MITRE • 02/26/2025
In the Linux kernel, the following vulnerability has been resolved:
cfi: Fix __cfi_slowpath_diag RCU usage with cpuidle
RCU_NONIDLE usage during __cfi_slowpath_diag can result in an invalid RCU state in the cpuidle code path:
WARNING: CPU: 1 PID: 0 at kernel/rcu/tree.c:613 rcu_eqs_enter+0xe4/0x138 ... Call trace: rcu_eqs_enter+0xe4/0x138 rcu_idle_enter+0xa8/0x100 cpuidle_enter_state+0x154/0x3a8 cpuidle_enter+0x3c/0x58 do_idle.llvm.6590768638138871020+0x1f4/0x2ec cpu_startup_entry+0x28/0x2c secondary_start_kernel+0x1b8/0x220 __secondary_switched+0x94/0x98
Instead, call rcu_irq_enter/exit to wake up RCU only when needed and disable interrupts for the entire CFI shadow/module check when we do.
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Analysis
by VulDB Data Team • 10/24/2025
The vulnerability described in CVE-2022-49709 represents a critical issue within the Linux kernel's control flow integrity implementation, specifically affecting the __cfi_slowpath_diag function's interaction with RCU (Read-Copy-Update) subsystem during cpuidle operations. This flaw manifests as an invalid RCU state when the kernel attempts to enter idle states, potentially leading to system instability and potential security implications. The issue occurs in the context of control flow integrity checking mechanisms that are designed to detect and prevent certain types of code injection and execution flow manipulation attacks. The vulnerability impacts the kernel's ability to properly manage RCU synchronization during CPU idle transitions, which are fundamental operations in power management and system stability.
The technical root cause of this vulnerability lies in the improper handling of RCU state management within the __cfi_slowpath_diag function when invoked during cpuidle code paths. Specifically, the function uses RCU_NONIDLE macros inappropriately, which can lead to inconsistent RCU state tracking and potential deadlocks or race conditions. The kernel's RCU subsystem maintains strict state tracking to ensure memory consistency during concurrent operations, and improper RCU state transitions during CPU idle entry can corrupt this tracking mechanism. This particular flaw demonstrates a failure in understanding the interaction between control flow integrity checking and the kernel's power management subsystem, where the RCU state management must be carefully coordinated with interrupt handling and CPU idle state transitions. The error trace indicates that the problem originates from rcu_eqs_enter function being called inappropriately during cpuidle entry, which violates fundamental RCU state transition rules.
The operational impact of this vulnerability extends beyond simple system instability to potentially compromise the kernel's security posture and overall system reliability. When the RCU subsystem enters an invalid state during CPU idle operations, it can lead to memory corruption, system hangs, or unpredictable behavior that might be exploited by malicious actors. The vulnerability affects the kernel's ability to properly handle CPU idle states, which are critical for power management and system performance optimization. This flaw could be particularly dangerous in server environments where power management and system stability are paramount, as it might cause unexpected system behavior during low-traffic periods when idle states are commonly entered. The issue also has implications for embedded systems and IoT devices that rely heavily on efficient power management and stable kernel operation. From an ATT&CK perspective, this vulnerability could enable privilege escalation or denial-of-service conditions that might be leveraged in broader attack campaigns.
The fix implemented for CVE-2022-49709 addresses the core issue by replacing the inappropriate RCU_NONIDLE usage with proper rcu_irq_enter/exit calls that only wake up RCU when necessary. This approach ensures that RCU state management is properly coordinated with interrupt handling and CPU idle state transitions, preventing the invalid RCU state that was causing the system instability. The solution also includes disabling interrupts for the entire CFI shadow/module check operation when required, which provides better synchronization guarantees during the critical code path execution. This mitigation strategy aligns with established kernel security practices and follows the principle of least privilege for RCU operations, ensuring that RCU synchronization is only activated when absolutely necessary. The fix demonstrates proper understanding of the interaction between control flow integrity checking, RCU subsystem requirements, and interrupt handling mechanisms. This vulnerability classification aligns with CWE-691, which addresses insufficient control flow integrity, and reflects the importance of proper state management in concurrent kernel subsystems. Organizations should prioritize applying this patch to maintain system stability and prevent potential exploitation of the RCU state corruption vulnerability.