CVE-2022-48816 in Linux
Summary
by MITRE • 07/16/2024
In the Linux kernel, the following vulnerability has been resolved:
SUNRPC: lock against ->sock changing during sysfs read
->sock can be set to NULL asynchronously unless ->recv_mutex is held. So it is important to hold that mutex. Otherwise a sysfs read can trigger an oops. Commit 17f09d3f619a ("SUNRPC: Check if the xprt is connected before handling sysfs reads") appears to attempt to fix this problem, but it only narrows the race window.
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Analysis
by VulDB Data Team • 10/06/2025
The vulnerability described in CVE-2022-48816 represents a critical race condition within the Linux kernel's sunrpc subsystem that specifically affects the Network File System (NFS) implementation. This issue manifests when asynchronous operations attempt to read sysfs attributes while the underlying socket connection is being modified, creating a scenario where the system can experience a kernel oops or system crash. The problem occurs in the context of the Remote Procedure Call (RPC) framework that enables distributed computing operations between networked systems, particularly affecting NFS client operations that rely on sunrpc for communication with remote servers.
The technical flaw stems from insufficient synchronization mechanisms when accessing the ->sock member variable during sysfs read operations. In the sunrpc subsystem, transport objects (xprt) maintain a reference to their underlying socket connection through the ->sock pointer. This pointer can be set to NULL asynchronously by other kernel threads handling connection management or cleanup operations, without proper locking. The vulnerability specifically occurs because the sysfs read operations do not properly acquire the ->recv_mutex lock that should protect access to the socket reference, creating a window where concurrent access can result in dereferencing a NULL pointer or accessing freed memory.
The operational impact of this vulnerability is significant as it can lead to system instability and potential denial of service conditions within NFS client environments. When a sysfs read operation occurs while the socket is being modified asynchronously, the kernel's memory management can encounter a critical error that results in a kernel oops, causing the system to crash or become unresponsive. This vulnerability is particularly dangerous in production environments where NFS services are heavily utilized, as it can disrupt file access operations and potentially affect multiple services dependent on network file systems. The race condition described in CVE-2022-48816 aligns with CWE-362, which identifies concurrent execution access to a shared resource without proper synchronization mechanisms, and represents a classic example of a race condition that can lead to system instability.
The attempted fix in commit 17f09d3f619a, while addressing the core issue, only narrows the race window rather than completely eliminating it, indicating the complexity of properly synchronizing asynchronous operations in kernel space. This partial fix demonstrates the challenges inherent in kernel-level concurrency control, where even seemingly simple race conditions can have profound implications for system stability. Organizations using NFS clients and systems that rely on sunrpc functionality are particularly vulnerable to this issue, as the vulnerability can be triggered by normal system operations during network activity or connection management. The mitigation strategy should involve applying the appropriate kernel security patches that properly implement the recv_mutex locking mechanism during sysfs read operations, ensuring that all access to the ->sock pointer is properly synchronized with potential asynchronous modifications to prevent the kernel oops condition that can result from improper memory access patterns.
This vulnerability also intersects with ATT&CK framework techniques related to privilege escalation and system stability compromise, as it can be exploited to cause system crashes or potentially enable more sophisticated attacks through system instability. The issue highlights the importance of proper kernel locking mechanisms in distributed systems and demonstrates how seemingly isolated race conditions can have cascading effects on system reliability and availability. The vulnerability serves as a reminder of the critical need for comprehensive testing of concurrent access patterns in kernel space, particularly in subsystems that handle network communication and distributed file access operations that are fundamental to modern enterprise computing environments.