Linux Kernel io_uring File Descriptor Use-After-Free

Executive Summary

This vulnerability in the Linux kernel involves a race condition in the io_uring subsystem. The function io_pipe_fixed() installs pipe ends in a fixed file table, drops a lock, and copies slot numbers to the application. If a fault occurs, the lock is reacquired and slots are cleared. However, if the request runs under io-wq, the lock is truly dropped between steps, exposing slots to other operations. By the time error handling occurs, slots may have been closed and reused by unrelated operations like IORING_OP_CLOSE or file updates, leading to unintended file removal from the table.

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Detection Guidance

This vulnerability is specific to the Linux kernel's io_uring subsystem and does not have a direct network detection method. Detection requires checking the kernel version and io_uring implementation. Use commands like 'uname -a' to check the kernel version and review io_uring-related logs or system calls for unusual activity.

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Impact Analysis

This vulnerability could allow an attacker to manipulate file operations in the Linux kernel, potentially causing system instability, unauthorized file access, or denial of service. If exploited, it might lead to crashes, data corruption, or privilege escalation on affected systems using io_uring.

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Mitigation Strategies

Update the Linux kernel to the latest stable version where this vulnerability is patched. Avoid using io_uring features if possible until the update is applied. Monitor system logs for signs of exploitation or unusual file operations.

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