GHSA-H9V2-7C48-MPXJ
Vulnerability from github – Published: 2026-09-11 21:31 – Updated: 2026-09-14 15:32In the Linux kernel, the following vulnerability has been resolved:
NFSD: Prevent lock owner use-after-free during client teardown
__destroy_client() releases a client's open owners, but a lock owner whose only reference is a blocked lock (nbl) stays on cl_ownerstr_hashtbl. client_has_state() does not count a bare owner, so DESTROY_CLIENTID can reach __destroy_client() with such owners present.
__destroy_client() then walks the table, calling remove_blocked_locks() on each owner without a reference. Freeing a blocked lock drops the owner reference held via flc_owner. The per-net laundromat reaps blocked locks from nn->blocked_locks_lru independently of client state. The two paths share blocked_locks_lock only for the list splice, not the owner's lifetime. The laundromat therefore frees the owner as __destroy_client() dereferences it, a NULL dereference in remove_blocked_locks().
nfsd4_release_lockowner() holds a reference across the same call; __destroy_client() does not. Hold cl_lock across the walk, taking a reference and unhashing each owner, then drop it before remove_blocked_locks() and nfs4_put_stateowner(), which take blocked_locks_lock and cl_lock.
{
"affected": [],
"aliases": [
"CVE-2026-89662"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-11T20:19:52Z",
"severity": "CRITICAL"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: Prevent lock owner use-after-free during client teardown\n\n__destroy_client() releases a client\u0027s open owners, but a lock owner\nwhose only reference is a blocked lock (nbl) stays on\ncl_ownerstr_hashtbl. client_has_state() does not count a bare owner,\nso DESTROY_CLIENTID can reach __destroy_client() with such owners\npresent.\n\n__destroy_client() then walks the table, calling remove_blocked_locks()\non each owner without a reference. Freeing a blocked lock drops the\nowner reference held via flc_owner. The per-net laundromat reaps\nblocked locks from nn-\u003eblocked_locks_lru independently of client state.\nThe two paths share blocked_locks_lock only for the list splice, not\nthe owner\u0027s lifetime. The laundromat therefore frees the owner as\n__destroy_client() dereferences it, a NULL dereference in\nremove_blocked_locks().\n\nnfsd4_release_lockowner() holds a reference across the same call;\n__destroy_client() does not. Hold cl_lock across the walk, taking a\nreference and unhashing each owner, then drop it before\nremove_blocked_locks() and nfs4_put_stateowner(), which take\nblocked_locks_lock and cl_lock.",
"id": "GHSA-h9v2-7c48-mpxj",
"modified": "2026-09-14T15:32:33Z",
"published": "2026-09-11T21:31:35Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89662"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1ce74d1b7770e69735e8f8e509807af4ff9c8ee7"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/42d7954b0a1907d4ef122aef94561952a033cdc3"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/4804c58f73a80d12df1de323bf97a164f6ee8743"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5e2fa29d223a9a1e6a948e40b109d09081d1decd"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8cf4ff0a7c083dd5e0067f517d63979b74b66649"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a6ead6fff3a7d03e49845f048f7000a2e0d34431"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b8bad5a11416b26cc7fd4b18fba46d75ff636558"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/bb38ff8b4dafbbd1781ad37cd96722fdf2cd972a"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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