io_uring: wake ring pollers for local task_work
With IORING_SETUP_DEFER_TASKRUN completions are queued as local work, and
only become CQEs when the submitter enters the kernel to wait for events.
For an application that finds out via poll() or epoll on the ring fd when
it is time to do that, io_uring_poll() reports EPOLLIN if local work is
pending.
That only helps if the work is there at the time of the call. When
DEFER_TASKRUN was added, io_req_local_work_add() did io_cqring_wake(),
which took care of tasks sleeping in poll() as well. Then polling got a
wait queue of its own, ->poll_wq, and the wake up in
io_req_local_work_add() was replaced by waking the submitter directly.
Since then ->poll_wq is only woken when CQEs are committed, which for
such a ring is done by the very task that is waiting to be told to:
submitter completion
poll(ring_fd)
io_uring_poll() // nothing yet
schedule()
io_req_local_work_add()
// ->cq_wait_nr: nobody waits
// sleeps on
Wake ->poll_wq when the first entry is put on the work list. Like for the
eventfd, that must not be done right away if the work is queued from a
wake up handler, as the chain of wake ups could get back to the wait
queue whose lock is held. Use an RCU callback in that case, with a
reference to the ring.
Analysis
Analysis and contextual insights are available on OpenCVE Cloud.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
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| Linux | Linux | affected |
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No data available yet.
No vendor fix or workaround currently provided.
Additional remediation guidance may be available on OpenCVE Cloud.
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Tue, 03 Nov 2026 12:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: io_uring: wake ring pollers for local task_work With IORING_SETUP_DEFER_TASKRUN completions are queued as local work, and only become CQEs when the submitter enters the kernel to wait for events. For an application that finds out via poll() or epoll on the ring fd when it is time to do that, io_uring_poll() reports EPOLLIN if local work is pending. That only helps if the work is there at the time of the call. When DEFER_TASKRUN was added, io_req_local_work_add() did io_cqring_wake(), which took care of tasks sleeping in poll() as well. Then polling got a wait queue of its own, ->poll_wq, and the wake up in io_req_local_work_add() was replaced by waking the submitter directly. Since then ->poll_wq is only woken when CQEs are committed, which for such a ring is done by the very task that is waiting to be told to: submitter completion poll(ring_fd) io_uring_poll() // nothing yet schedule() io_req_local_work_add() // ->cq_wait_nr: nobody waits // sleeps on Wake ->poll_wq when the first entry is put on the work list. Like for the eventfd, that must not be done right away if the work is queued from a wake up handler, as the chain of wake ups could get back to the wait queue whose lock is held. Use an RCU callback in that case, with a reference to the ring. | |
| Title | io_uring: wake ring pollers for local task_work | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-11-03T11:48:17.911Z
Reserved: 2026-09-25T10:25:14.404Z
Link: CVE-2026-99268
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-11-03T12:17:33.980
Modified: 2026-11-03T12:17:33.980
Link: CVE-2026-99268
Redhat
No data.
OpenCVE Enrichment
No data.
No weakness.