CVE-2023-52895 in Linux
Summary
by MITRE • 08/21/2024
In the Linux kernel, the following vulnerability has been resolved:
io_uring/poll: don't reissue in case of poll race on multishot request
A previous commit fixed a poll race that can occur, but it's only applicable for multishot requests. For a multishot request, we can safely ignore a spurious wakeup, as we never leave the waitqueue to begin with.
A blunt reissue of a multishot armed request can cause us to leak a buffer, if they are ring provided. While this seems like a bug in itself, it's not really defined behavior to reissue a multishot request directly. It's less efficient to do so as well, and not required to rearm anything like it is for singleshot poll requests.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 02/17/2026
The vulnerability identified as CVE-2023-52895 affects the Linux kernel's io_uring subsystem, specifically addressing a race condition in poll handling for multishot requests. This issue resides within the kernel's asynchronous I/O framework that provides high-performance I/O operations through the io_uring interface. The problem manifests when dealing with multishot polling requests where the kernel's polling mechanism encounters a race condition during request processing. According to CWE-362, this represents a concurrent execution race condition that can lead to improper resource handling and potential security implications.
The technical flaw occurs when a multishot io_uring request experiences a poll race condition, which is a scenario where multiple threads or processes access shared resources simultaneously, causing unpredictable behavior. The kernel's previous fix for this race condition was only applied to multishot requests, but the implementation contained a critical oversight. When a multishot request is armed and subsequently reissued, the system can leak buffers that were provided by the ring, particularly when these buffers are ring-provided. This represents a resource leak vulnerability that can accumulate over time and potentially lead to system instability or denial of service conditions.
The operational impact of this vulnerability extends beyond simple resource consumption as it affects the fundamental correctness of the io_uring subsystem's buffer management. When a multishot request is incorrectly reissued, the system fails to properly track and release ring-provided buffers, leading to memory leaks that can degrade system performance. The issue is particularly concerning because it occurs in the kernel's core I/O handling path, meaning any application utilizing io_uring for high-performance I/O operations could be affected. This vulnerability aligns with ATT&CK technique T1070.004, which involves the use of system scripts and commands to hide or manipulate system resources, as the buffer leakage could potentially be exploited to exhaust system resources.
The fix implemented addresses the specific scenario where multishot requests are reissued inappropriately, recognizing that for multishot requests, spurious wakeups should be safely ignored since these requests never leave the waitqueue. This approach prevents the problematic reissue behavior that leads to buffer leaks while maintaining the correct semantics of multishot polling. The solution emphasizes that reissuing multishot requests directly is not defined behavior, making the approach less efficient and unnecessary compared to how singleshot poll requests are handled. The mitigation strategy focuses on preventing the erroneous reissue of multishot requests, which aligns with the principle of least privilege and proper resource management. This fix ensures that ring-provided buffers are properly managed and released, preventing the accumulation of leaked resources that could otherwise lead to system instability or resource exhaustion attacks.
The vulnerability demonstrates the complexity of kernel-level race condition handling and the importance of careful buffer management in high-performance I/O subsystems. The io_uring subsystem's design must account for various edge cases in concurrent access patterns while maintaining performance characteristics. This issue highlights the critical need for thorough testing of concurrent scenarios in kernel code and the potential for seemingly minor implementation details to have significant impacts on system stability and resource management. The fix reinforces the importance of understanding the specific semantics of different request types within kernel subsystems and implementing appropriate safeguards for each category of operation.