CVE-2024-42152 in Linux
Summary
by MITRE • 07/30/2024
In the Linux kernel, the following vulnerability has been resolved:
nvmet: fix a possible leak when destroy a ctrl during qp establishment
In nvmet_sq_destroy we capture sq->ctrl early and if it is non-NULL we know that a ctrl was allocated (in the admin connect request handler) and we need to release pending AERs, clear ctrl->sqs and sq->ctrl (for nvme-loop primarily), and drop the final reference on the ctrl.
However, a small window is possible where nvmet_sq_destroy starts (as a result of the client giving up and disconnecting) concurrently with the nvme admin connect cmd (which may be in an early stage). But *before* kill_and_confirm of sq->ref (i.e. the admin connect managed to get an sq live reference). In this case, sq->ctrl was allocated however after it was captured in a local variable in nvmet_sq_destroy. This prevented the final reference drop on the ctrl.
Solve this by re-capturing the sq->ctrl after all inflight request has completed, where for sure sq->ctrl reference is final, and move forward based on that.
This issue was observed in an environment with many hosts connecting multiple ctrls simoutanuosly, creating a delay in allocating a ctrl leading up to this race window.
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Analysis
by VulDB Data Team • 07/19/2025
The vulnerability identified as CVE-2024-42152 affects the Linux kernel's NVMe over Fabrics target implementation, specifically within the nvmet subsystem responsible for managing NVMe target connections. This issue represents a memory management race condition that can lead to resource leaks and potential system instability. The flaw occurs during the destruction of controller (ctrl) objects when handling queue pair (qp) establishment processes, creating a scenario where controller references are not properly released due to concurrent operations. The vulnerability stems from improper handling of controller lifecycle management during connection termination phases, particularly when client disconnections occur simultaneously with admin connect command processing.
The technical flaw manifests in the nvmet_sq_destroy function where the system captures the sq->ctrl reference early in the destruction process. When a controller object exists and is non-NULL, the system should release pending Asynchronous Event Requests (AERs), clear controller queues, and drop the final reference on the controller. However, a race condition exists where nvmet_sq_destroy begins execution while an admin connect command is in progress but has not yet completed its reference acquisition. Specifically, the admin connect command manages to obtain a live reference to the queue pair before the destruction process can fully complete its reference handling. This creates a window where the controller reference is allocated but not properly accounted for during the final cleanup phase, preventing the proper release of controller resources. The issue is classified under CWE-362, representing a race condition in resource management, and aligns with ATT&CK technique T1499.004 for resource exhaustion attacks.
The operational impact of this vulnerability extends beyond simple memory leaks to potentially affect system stability and performance in high-concurrency environments. When multiple hosts simultaneously connect and establish multiple controllers, the timing window for this race condition increases significantly, creating conditions where controller resources accumulate without proper cleanup. This can lead to progressive memory consumption, eventual system resource exhaustion, and potential denial of service conditions for legitimate NVMe target operations. The vulnerability is particularly concerning in enterprise storage environments where NVMe over Fabrics is heavily utilized, as it can cause gradual degradation of system performance and reliability. The issue demonstrates how seemingly isolated race conditions in kernel subsystems can compound under stress conditions to create significant operational risks.
Mitigation strategies for CVE-2024-42152 involve both immediate kernel updates and operational monitoring approaches. The primary solution requires applying the patched kernel version that implements the corrected reference capture mechanism, ensuring that sq->ctrl is re-captured after all inflight requests have completed to guarantee a final reference state. Organizations should prioritize kernel updates in production environments, particularly those running NVMe target services with high connection concurrency. Additionally, system administrators should monitor for unusual memory consumption patterns and controller reference accumulation in NVMe target subsystems. Implementing proper connection rate limiting and monitoring for concurrent connection attempts can help reduce exposure to this race condition. The fix addresses the underlying race condition through proper synchronization mechanisms and ensures that all controller references are properly accounted for regardless of the timing of concurrent operations, thereby preventing the accumulation of unreleased controller resources that could lead to system instability.