CVE-2026-80920

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CVE-2026-80920

Summary: io_uring: defer eventfd signaling when queued from a wakeup handler

Details: In the Linux kernel, the following vulnerability has been resolved: io_uring: defer eventfd signaling when queued from a wakeup handler io_req_local_work_add() signals the CQ ring eventfd inline when it is the one to push the first entry onto ->work_list. For DEFER_TASKRUN rings that add is frequently done from a waitqueue wakeup handler, where an arbitrary waitqueue lock is held. eventfd_signal_mask() only refuses to recurse when current->in_eventfd is set, but that bit is set by eventfd_signal_mask() itself. If the wake chain starts somewhere else, signal goes out inline and can feed back into epoll. Add IOU_F_TWQ_IN_WAKE, set it on the task_work add done from the three waitqueue callbacks, and use it to force io_eventfd_signal() down the existing call_rcu_hurry() deferral instead of signaling inline.

References: https://git.kernel.org/stable/c/40b6ccf68731809ceb85c6e9f0f8f2ed61c7aa5a, https://git.kernel.org/stable/c/b6bb334b0e9348887e3e55e1f494b0c3b8fbf59f, https://git.kernel.org/stable/c/cd305ee3633a45fcf5f3a5d83f99f3cb77d87b6e, https://git.kernel.org/stable/c/e22f4494cc9487d326e5e3067f33dea7c1e442b2, https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80920.json, https://nvd.nist.gov/vuln/detail/CVE-2026-80920, https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git