CVE-2024-38545 in Linux
Summary
by MITRE • 06/19/2024
In the Linux kernel, the following vulnerability has been resolved:
RDMA/hns: Fix UAF for cq async event
The refcount of CQ is not protected by locks. When CQ asynchronous events and CQ destruction are concurrent, CQ may have been released, which will cause UAF.
Use the xa_lock() to protect the CQ refcount.
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Analysis
by VulDB Data Team • 10/04/2025
The vulnerability identified as CVE-2024-38545 resides within the Linux kernel's RDMA/hns subsystem, specifically affecting the handling of Completion Queues (CQ) during asynchronous event processing and concurrent destruction operations. This issue represents a critical race condition that can lead to use-after-free conditions, fundamentally compromising system stability and security. The vulnerability manifests when multiple threads or processes attempt to simultaneously process asynchronous events for a Completion Queue while another operation attempts to destroy that same queue, creating a scenario where memory management becomes inconsistent and potentially exploitable.
The technical flaw stems from inadequate synchronization mechanisms protecting the reference count of Completion Queues within the Hardware Network Subsystem (hns) driver. The CQ reference count is not adequately protected by locks, creating a window where concurrent operations can lead to improper memory management. When asynchronous events are processed concurrently with CQ destruction, the system may attempt to access memory that has already been freed, resulting in undefined behavior that can manifest as system crashes, memory corruption, or potentially exploitable conditions. This type of vulnerability falls under the CWE-367 weakness category, specifically addressing Time-of-Check to Time-of-Use (TOCTOU) race conditions where the state of a resource changes between when it is checked and when it is used.
The operational impact of this vulnerability extends beyond simple system instability, as it can affect RDMA (Remote Direct Memory Access) operations that are critical for high-performance computing environments, data center networking, and storage systems. Systems utilizing the hns driver for network acceleration may experience unexpected termination of network operations, data loss, or complete system crashes when concurrent CQ operations occur. The vulnerability is particularly concerning in environments where RDMA is used for low-latency communication patterns, as the timing and frequency of concurrent operations can increase the likelihood of triggering this race condition. Attackers could potentially exploit this condition to cause denial of service or, in more sophisticated scenarios, achieve privilege escalation through memory corruption techniques.
The fix implemented addresses the root cause by introducing proper locking mechanisms through the use of xa_lock() to protect the CQ reference count operations. This solution ensures that all modifications to the completion queue reference count are properly synchronized, preventing concurrent access that could lead to premature release of memory resources. The mitigation strategy aligns with established security practices for concurrent programming and follows the ATT&CK framework's approach to defending against race condition vulnerabilities in kernel space operations. The solution demonstrates proper resource management principles and reinforces the importance of lock-based synchronization in multi-threaded kernel subsystems. Organizations should prioritize applying this patch to all systems running affected kernel versions, particularly those operating in high-throughput networking environments where RDMA operations are prevalent. The fix also serves as a reminder of the critical importance of proper synchronization in kernel-level code and the potential security implications of race conditions in system drivers.