{"cve":"CVE-2021-47391","nvd":{"published":"2024-05-21T15:15:24.480","modified":"2026-08-04T10:17:01.443","status":"Modified","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nRDMA/cma: Ensure rdma_addr_cancel() happens before issuing more requests\n\nThe FSM can run in a circle allowing rdma_resolve_ip() to be called twice\non the same id_priv. While this cannot happen without going through the\nwork, it violates the invariant that the same address resolution\nbackground request cannot be active twice.\n\n       CPU 1                                  CPU 2\n\nrdma_resolve_addr():\n  RDMA_CM_IDLE -> RDMA_CM_ADDR_QUERY\n  rdma_resolve_ip(addr_handler)  #1\n\n\t\t\t process_one_req(): for #1\n                          addr_handler():\n                            RDMA_CM_ADDR_QUERY -> RDMA_CM_ADDR_BOUND\n                            mutex_unlock(&id_priv->handler_mutex);\n                            [.. handler still running ..]\n\nrdma_resolve_addr():\n  RDMA_CM_ADDR_BOUND -> RDMA_CM_ADDR_QUERY\n  rdma_resolve_ip(addr_handler)\n    !! two requests are now on the req_list\n\nrdma_destroy_id():\n destroy_id_handler_unlock():\n  _destroy_id():\n   cma_cancel_operation():\n    rdma_addr_cancel()\n\n                          // process_one_req() self removes it\n\t\t          spin_lock_bh(&lock);\n                           cancel_delayed_work(&req->work);\n\t                   if (!list_empty(&req->list)) == true\n\n      ! rdma_addr_cancel() returns after process_on_req #1 is done\n\n   kfree(id_priv)\n\n\t\t\t process_one_req(): for #2\n                          addr_handler():\n\t                    mutex_lock(&id_priv->handler_mutex);\n                            !! Use after free on id_priv\n\nrdma_addr_cancel() expects there to be one req on the list and only\ncancels the first one. The self-removal behavior of the work only happens\nafter the handler has returned. This yields a situations where the\nreq_list can have two reqs for the same \"handle\" but rdma_addr_cancel()\nonly cancels the first one.\n\nThe second req remains active beyond rdma_destroy_id() and will\nuse-after-free id_priv once it inevitably triggers.\n\nFix this by remembering if the id_priv has called rdma_resolve_ip() and\nalways cancel before calling it again. This ensures the req_list never\ngets more than one item in it and doesn't cost anything in the normal flow\nthat never uses this strange error path.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.8},"cwes":["CWE-416"],"references":["https://git.kernel.org/stable/c/03d884671572af8bcfbc9e63944c1021efce7589","https://git.kernel.org/stable/c/305d568b72f17f674155a2a8275f865f207b3808","https://git.kernel.org/stable/c/9a085fa9b7d644a234465091e038c1911e1a4f2a","https://git.kernel.org/stable/c/03d884671572af8bcfbc9e63944c1021efce7589","https://git.kernel.org/stable/c/305d568b72f17f674155a2a8275f865f207b3808"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T21:50:30.954589733+00:00"},"epss":{"cve":"CVE-2021-47391","score":0.00243,"percentile":0.15592,"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."]}