{"id":"CVE-2026-64262","summary":"fuse-uring: end fuse_req on io-uring cancel task work","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nfuse-uring: end fuse_req on io-uring cancel task work\n\nWhen io_uring delivers task work with tw.cancel set (PF_EXITING,\nPF_KTHREAD fallback, or percpu_ref_is_dying on the ring context),\nfuse_uring_send_in_task() takes the cancel branch, assigns\n-ECANCELED, and falls through to fuse_uring_send(). That path only\nflips the entry to FRRS_USERSPACE and completes the io_uring cmd;\nit never discharges the ring entry's owning reference to the\nfuse_req that fuse_uring_add_req_to_ring_ent() handed it at\ndispatch time.\n\n    fuse_uring_send_in_task()\n      tw.cancel == true\n        err = -ECANCELED\n      fuse_uring_send(ent, cmd, err, issue_flags)\n        ent-\u003estate = FRRS_USERSPACE\n        list_move(&ent-\u003elist, &queue-\u003eent_in_userspace)\n        ent-\u003ecmd = NULL\n        io_uring_cmd_done(-ECANCELED)\n        /* ent-\u003efuse_req still set, req still hashed */\n\nThe fuse_req stays linked on fpq-\u003eprocessing[hash] and\nfuse_request_end() is never invoked. The originating syscall\nthread blocks in D-state in request_wait_answer() until\nfuse_abort_conn() runs, which can be the entire connection\nlifetime. For FR_BACKGROUND requests fc-\u003enum_background is never\ndecremented either, so repeated cancels inflate the counter until\nmax_background is hit and all later background ops stall. tw.cancel does\nnot imply a connection abort (e.g. a single io_uring worker thread exits\nwhile the fuse connection stays up), so this cannot be left for\nfuse_abort_conn() to clean up.\n\nEnding the req but still routing the entry through fuse_uring_send()\nis not enough: that leaves a req-less entry on ent_in_userspace, and\nent_list_request_expired() dereferences ent-\u003efuse_req unconditionally\non the head of that list, which would then NULL-deref.\n\nFix the cancel branch to release the entry directly. Remove it from the\nqueue, complete the io_uring cmd, end the fuse_req, free the entry, and\ndrop its queue_refs (waking the teardown waiter if it was the last).","modified":"2026-08-18T03:30:51.769317170Z","published":"2026-07-25T08:49:12.599Z","related":["openSUSE-SU-2026:11476-1"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64262.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/4f45f276d5b4412eade6f74f2e37f3adba0473ed"},{"type":"WEB","url":"https://git.kernel.org/stable/c/bb476ef8e1027a9d509fbaaf81f5061a07e9e5a7"},{"type":"WEB","url":"https://git.kernel.org/stable/c/bea4fe98204b6ce7eb8e29f7bf867dd7619b3ddd"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64262.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-64262"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"c2c9af9a0b13261c36909036057a116f2edb5e1a"},{"fixed":"bb476ef8e1027a9d509fbaaf81f5061a07e9e5a7"},{"fixed":"4f45f276d5b4412eade6f74f2e37f3adba0473ed"},{"fixed":"bea4fe98204b6ce7eb8e29f7bf867dd7619b3ddd"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-64262.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.14.0"},{"fixed":"6.18.39"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.1.4"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-64262.json"}}],"schema_version":"1.9.0"}