Bug 2565272 (CVE-2026-99228)
| Summary: | CVE-2026-99228 kernel: kernel: Denial of Service via io_uring worker hang during thread exit | ||
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| Product: | [Other] Security Response | Reporter: | OSIDB Bzimport <bzimport> |
| Component: | vulnerability | Assignee: | Product Security DevOps Team <prodsec-dev> |
| Status: | NEW --- | QA Contact: | |
| Severity: | low | Docs Contact: | |
| Priority: | low | ||
| Version: | unspecified | CC: | akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers |
| Target Milestone: | --- | Keywords: | Security |
| Target Release: | --- | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | --- | |
| Doc Text: |
A flaw was found in the Linux kernel's io_uring subsystem. When an application thread exits while running asynchronous operations via internal worker queues, the signal intended to interrupt and terminate worker tasks can be lost. A local user could exploit this vulnerability by submitting asynchronous requests that block waiting for an external event, such as opening a named pipe without a peer, causing the exiting thread to hang indefinitely and leading to a Denial of Service (DoS).
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Story Points: | --- |
| Clone Of: | Environment: | ||
| Last Closed: | Type: | --- | |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
In the Linux kernel, the following vulnerability has been resolved: io_uring/io-wq: don't lose the signal that ends work When a thread exits, only its tracked requests are cancelled. Then its io-wq is torn down. io_wq_exit_workers() signals every worker, to get it out of an interruptible sleep, and waits for all of them to exit. Before they do, they go through the work that is left. Unbounded work is cancelled. Bounded work is run, as it is expected to end by itself. Not all of it does. An open has no file yet, so it counts as bounded, and the open of a FIFO waits for the other end. That is what the signal is for. But the workers are signalled once, and a worker that hasn't started the work by then loses the signal: io_wq_exit_workers() io_worker_handle_work() io_wq_worker_wake() set TIF_NOTIFY_SIGNAL io_assign_current_work() io_run_task_work() clear TIF_NOTIFY_SIGNAL io_wq_submit_work() fifo_open() wait_for_partner() wait_for_completion_timeout() The thread never gets out of do_exit(): IORING_OP_OPENAT of a FIFO without a writer, IOSQE_ASYNC exit of the thread that has submitted it hangs in more than 9 of 10 attempts (4 CPUs, KVM), until the process is killed. Set TIF_NOTIFY_SIGNAL for bounded work that is started with IO_WQ_BIT_EXIT set. The bit is set before the workers are signalled, and it is tested after the flag has been cleared, with clear_notify_signal() providing the barrier. So either the flag stays, or the bit is seen. Work that is started while the io-wq exits is treated like work that is being run at that time: it isn't interrupted unless it waits interruptibly.