GHSA-7JRM-G6VX-3834
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: revoke copy-notify stateids before dropping their reference
Copy-notify stateids live in the s2s_cp_stateids IDR and on their parent stid's sc_cp_list, pinned by a single membership reference. _free_cpntf_state_locked() only unlinks an entry once its refcount reaches zero, so any revoke path that runs while a concurrent find_cpntf_state()/manage_cpntf_state() holder has elevated cs_count drops the reference without unlinking, leaving the entry discoverable with its membership reference already consumed. A second revoke or a laundromat tick then frees it while the reader still holds the pointer -- a KASAN-detectable use-after-free at the reader's nfs4_put_cpntf_state().
This affected all three revoke paths:
-
The parent-stid drain (nfs4_free_cpntf_statelist()) repeatedly called _free_cpntf_state_locked() on the first list entry; a holder that had bumped cs_count made it return early, so the next iteration re-decremented and burned the holder's reference.
-
OFFLOAD_CANCEL (manage_cpntf_state()) and laundromat expiry likewise used _free_cpntf_state_locked() and could drop 2->1 without unlinking.
Add revoke_cpntf_state_locked(), which unhashes the entry from the IDR and sc_cp_list first (deferring the final free to any holder), and use it from all three revoke paths. The drain now walks with list_for_each_entry_safe() and revokes each entry unconditionally, so it terminates in one pass per entry regardless of cs_count. The unhash is gated on !list_empty(&cps->cp_list); the idr_remove() gate matters because idr_alloc_cyclic() may have recycled the so_id by then. Keep _free_cpntf_state_locked() for the reference-holder put path only, where a concurrent revoke may already have unlinked the entry (its list_del_init() then a no-op).
{
"affected": [],
"aliases": [
"CVE-2026-89663"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-11T20:19:52Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: revoke copy-notify stateids before dropping their reference\n\nCopy-notify stateids live in the s2s_cp_stateids IDR and on their parent\nstid\u0027s sc_cp_list, pinned by a single membership reference.\n_free_cpntf_state_locked() only unlinks an entry once its refcount reaches\nzero, so any revoke path that runs while a concurrent\nfind_cpntf_state()/manage_cpntf_state() holder has elevated cs_count drops\nthe reference without unlinking, leaving the entry discoverable with its\nmembership reference already consumed. A second revoke or a laundromat tick\nthen frees it while the reader still holds the pointer -- a\nKASAN-detectable use-after-free at the reader\u0027s nfs4_put_cpntf_state().\n\nThis affected all three revoke paths:\n\n - The parent-stid drain (nfs4_free_cpntf_statelist()) repeatedly called\n _free_cpntf_state_locked() on the first list entry; a holder that had\n bumped cs_count made it return early, so the next iteration\n re-decremented and burned the holder\u0027s reference.\n\n - OFFLOAD_CANCEL (manage_cpntf_state()) and laundromat expiry likewise\n used _free_cpntf_state_locked() and could drop 2-\u003e1 without unlinking.\n\nAdd revoke_cpntf_state_locked(), which unhashes the entry from the IDR and\nsc_cp_list first (deferring the final free to any holder), and use it from\nall three revoke paths. The drain now walks with list_for_each_entry_safe()\nand revokes each entry unconditionally, so it terminates in one pass per\nentry regardless of cs_count. The unhash is gated on\n!list_empty(\u0026cps-\u003ecp_list); the idr_remove() gate matters because\nidr_alloc_cyclic() may have recycled the so_id by then. Keep\n_free_cpntf_state_locked() for the reference-holder put path only, where a\nconcurrent revoke may already have unlinked the entry (its list_del_init()\nthen a no-op).",
"id": "GHSA-7jrm-g6vx-3834",
"modified": "2026-09-14T15:32:33Z",
"published": "2026-09-11T21:31:35Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89663"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/06a62f6dbc60791f4229c6950b1eec6b18df9af1"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3b0c3595db99bb4bebd7c8aa8a36f3c50e411bb7"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5f00e0ab4de45d4f9e4bd0883cf2517acf63fc0d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/6b8149448cdcb476fba4559d1ecc247efee9971b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a1fca0f7bbb7b100a39c7ba8dd7922c87c4237a3"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b56d2c5f01cddbeca7d11cce81d97db4ec9a464f"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/caddbeffab1eaba1d2bcf5ceda35547863466705"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ff8a3cff02b92b2a82f1a9876038fcf953ae9c25"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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