CVE-2026-80920io_uring: defer eventfd signaling when queued from a wakeup handler

Official description

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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/d0c240f25e654442a72af5ca021a02165ccce638
• https://git.kernel.org/stable/c/9d984451baf768ecd9e1fdad4637b729fcb2c9d5
• https://git.kernel.org/stable/c/e22f4494cc9487d326e5e3067f33dea7c1e442b2
• https://git.kernel.org/stable/c/b6bb334b0e9348887e3e55e1f494b0c3b8fbf59f
• https://git.kernel.org/stable/c/40b6ccf68731809ceb85c6e9f0f8f2ed61c7aa5a
• https://git.kernel.org/stable/c/cd305ee3633a45fcf5f3a5d83f99f3cb77d87b6e