EUVD-2026-18746
GHSA-c5mp-x9x5-3g5v
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3Description
In the Linux kernel, the following vulnerability has been resolved: io_uring/poll: fix multishot recv missing EOF on wakeup race When a socket send and shutdown() happen back-to-back, both fire wake-ups before the receiver's task_work has a chance to run. The first wake gets poll ownership (poll_refs=1), and the second bumps it to 2. When io_poll_check_events() runs, it calls io_poll_issue() which does a recv that reads the data and returns IOU_RETRY. The loop then drains all accumulated refs (atomic_sub_return(2) -> 0) and exits, even though only the first event was consumed. Since the shutdown is a persistent state change, no further wakeups will happen, and the multishot recv can hang forever. Check specifically for HUP in the poll loop, and ensure that another loop is done to check for status if more than a single poll activation is pending. This ensures we don't lose the shutdown event.
Analysis
Linux kernel io_uring/poll multishot recv can hang indefinitely when a socket shutdown occurs concurrently with data reception, due to a race condition where accumulated poll wakeups are drained without consuming the persistent HUP event. The vulnerability affects all Linux kernel versions with io_uring poll support and requires a fix to explicitly check for HUP conditions and re-loop when multiple poll activations are pending.
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