{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-89681", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.748Z", "datePublished": "2026-09-11T19:46:04.121Z", "dateUpdated": "2026-10-19T08:50:54.644Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:50:54.644Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: fix layout fence worker double-reference race\n\nThe workqueue core clears WORK_STRUCT_PENDING before the callback\nis invoked, so delayed_work_pending() in lm_breaker_timedout() can\nreturn false while the fence worker is already running. This lets\nthe breaker take a duplicate sc_count reference and schedule a new\nworker that coalesces with the in-progress one. The extra reference\nis never put, leaking the layout stateid.\n\nReplace the racy delayed_work_pending() check with an\nls_fence_inflight boolean set atomically with\nrefcount_inc_not_zero() under ls_lock, and cleared under ls_lock\nbefore the final nfs4_put_stid() on the dispose path; the retry\npath intentionally retains it. Remove the self-rearm\nmod_delayed_work() at the top of the worker." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL" }, "scenarios": [ { "lang": "en", "value": "AV:N - The flaw is in nfsd pNFS SCSI layout fencing (nfsd4_layout_lm_breaker_timedout → nfsd4_layout_fence_worker in fs/nfsd/nfs4layouts.c), reached over NFSv4.1 COMPOUND on TCP/2049: LAYOUTGET installs an FL_LAYOUT lease, then a conflicting OPEN/WRITE hits nfsd_open_break_lease → time_out_leases after recall timeout.\nAC:L - The attacker controls both sides of the delayed_work_pending race: one client holds a SCSI layout and ignores CB_LAYOUTRECALL so the fence worker runs, while other attacker connections spam OPEN/WRITE so concurrent nfsd threads call lm_breaker_timedout while WORK_STRUCT_PENDING is already clear; the sequence is retryable.\nPR:N - Typical nfsd exports accept AUTH_SYS/AUTH_NULL with no cryptographic RPC authentication; EXCHANGE_ID, CREATE_SESSION, OPEN, and LAYOUTGET succeed for any host permitted by the export, so a remote NFSv4.1 client needs no kernel-verified credentials or local account on the server.\nUI:N - The attacker is the NFS client and sends LAYOUTGET plus conflicting OPEN/WRITE compounds against an already-running pNFS SCSI export; no victim user must mount a filesystem, open a file, or take any other action on the host.\nS:U - Impact is kernel nfsd layout-stateid and nfs4_client lifetime on the NFS server host and does not cross a VM, hypervisor, sandbox, or IOMMU security boundary.\nC:H - The unmatched sc_count leaves the nfs4_layout_stateid on nfs4_file.fi_lo_states without pinning nfs4_client; after that client is expired, a later LAYOUTGET walks the list and nfsd4_run_cb dereferences freed cb_clp, a use-after-free that can be reused for arbitrary kernel reads.\nI:H - The same use-after-free of nfs4_client (cl_cb_session, cl_callback_wq, and nfsd4_callback_ops) from nfsd4_recall_file_layout → nfsd4_run_cb enables heap spraying and function-pointer hijack of the CB_LAYOUTRECALL work path.\nA:H - Each won race permanently leaks a layout stateid (and can pin nfs4_client via cl_lo_states); repeating LAYOUTGET/fence races exhausts nfsd state and kernel memory, and the later nfs4_client use-after-free oopses or panics the nfsd thread." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/nfsd/nfs4layouts.c", "fs/nfsd/state.h" ], "versions": [ { "version": "f52792f484ba2316853736856dde19b7e7458861", "lessThan": "a278d361e0e8f242211891193d56483a7a9f47a8", "status": "affected", "versionType": "git" }, { "version": "f52792f484ba2316853736856dde19b7e7458861", "lessThan": "8580571227451384399b3fa53fcde19848c48e5a", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/nfsd/nfs4layouts.c", "fs/nfsd/state.h" ], "versions": [ { "version": "7.1", "status": "affected" }, { "version": "0", "lessThan": "7.1", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.4", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.1", "versionEndExcluding": "7.2.4" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.1", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/a278d361e0e8f242211891193d56483a7a9f47a8" }, { "url": "https://git.kernel.org/stable/c/8580571227451384399b3fa53fcde19848c48e5a" } ], "title": "nfsd: fix layout fence worker double-reference race", "x_generator": { "engine": "bippy-1.2.0" } } } }