{"cve":"CVE-2021-46942","nvd":{"published":"2024-02-27T19:04:06.017","modified":"2026-06-17T04:15:55.907","status":"Modified","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nio_uring: fix shared sqpoll cancellation hangs\n\n[  736.982891] INFO: task iou-sqp-4294:4295 blocked for more than 122 seconds.\n[  736.982897] Call Trace:\n[  736.982901]  schedule+0x68/0xe0\n[  736.982903]  io_uring_cancel_sqpoll+0xdb/0x110\n[  736.982908]  io_sqpoll_cancel_cb+0x24/0x30\n[  736.982911]  io_run_task_work_head+0x28/0x50\n[  736.982913]  io_sq_thread+0x4e3/0x720\n\nWe call io_uring_cancel_sqpoll() one by one for each ctx either in\nsq_thread() itself or via task works, and it's intended to cancel all\nrequests of a specified context. However the function uses per-task\ncounters to track the number of inflight requests, so it counts more\nrequests than available via currect io_uring ctx and goes to sleep for\nthem to appear (e.g. from IRQ), that will never happen.\n\nCancel a bit more than before, i.e. all ctxs that share sqpoll\nand continue to use shared counters. Don't forget that we should not\nremove ctx from the list before running that task_work sqpoll-cancel,\notherwise the function wouldn't be able to find the context and will\nhang.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":5.5},"cwes":[],"references":["https://git.kernel.org/stable/c/734551df6f9bedfbefcd113ede665945e9de0b99","https://git.kernel.org/stable/c/cb5e0b3d0f993a6268c1a2c7ede2f9aa0c17ef68","https://git.kernel.org/stable/c/734551df6f9bedfbefcd113ede665945e9de0b99","https://git.kernel.org/stable/c/cb5e0b3d0f993a6268c1a2c7ede2f9aa0c17ef68"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T21:45:59.823092188+00:00"},"epss":{"cve":"CVE-2021-46942","score":0.00193,"percentile":0.09071,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}