GHSA-QWRM-23W5-G55V
Vulnerability from github – Published: 2025-05-09 09:33 – Updated: 2025-11-12 21:31In the Linux kernel, the following vulnerability has been resolved:
nfsd: decrease sc_count directly if fail to queue dl_recall
A deadlock warning occurred when invoking nfs4_put_stid following a failed dl_recall queue operation: T1 T2 nfs4_laundromat nfs4_get_client_reaplist nfs4_anylock_blockers __break_lease spin_lock // ctx->flc_lock spin_lock // clp->cl_lock nfs4_lockowner_has_blockers locks_owner_has_blockers spin_lock // flctx->flc_lock nfsd_break_deleg_cb nfsd_break_one_deleg nfs4_put_stid refcount_dec_and_lock spin_lock // clp->cl_lock
When a file is opened, an nfs4_delegation is allocated with sc_count initialized to 1, and the file_lease holds a reference to the delegation. The file_lease is then associated with the file through kernel_setlease.
The disassociation is performed in nfsd4_delegreturn via the following call chain: nfsd4_delegreturn --> destroy_delegation --> destroy_unhashed_deleg --> nfs4_unlock_deleg_lease --> kernel_setlease --> generic_delete_lease The corresponding sc_count reference will be released after this disassociation.
Since nfsd_break_one_deleg executes while holding the flc_lock, the disassociation process becomes blocked when attempting to acquire flc_lock in generic_delete_lease. This means: 1) sc_count in nfsd_break_one_deleg will not be decremented to 0; 2) The nfs4_put_stid called by nfsd_break_one_deleg will not attempt to acquire cl_lock; 3) Consequently, no deadlock condition is created.
Given that sc_count in nfsd_break_one_deleg remains non-zero, we can safely perform refcount_dec on sc_count directly. This approach effectively avoids triggering deadlock warnings.
{
"affected": [],
"aliases": [
"CVE-2025-37871"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-05-09T07:16:08Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: decrease sc_count directly if fail to queue dl_recall\n\nA deadlock warning occurred when invoking nfs4_put_stid following a failed\ndl_recall queue operation:\n T1 T2\n nfs4_laundromat\n nfs4_get_client_reaplist\n nfs4_anylock_blockers\n__break_lease\n spin_lock // ctx-\u003eflc_lock\n spin_lock // clp-\u003ecl_lock\n nfs4_lockowner_has_blockers\n locks_owner_has_blockers\n spin_lock // flctx-\u003eflc_lock\n nfsd_break_deleg_cb\n nfsd_break_one_deleg\n nfs4_put_stid\n refcount_dec_and_lock\n spin_lock // clp-\u003ecl_lock\n\nWhen a file is opened, an nfs4_delegation is allocated with sc_count\ninitialized to 1, and the file_lease holds a reference to the delegation.\nThe file_lease is then associated with the file through kernel_setlease.\n\nThe disassociation is performed in nfsd4_delegreturn via the following\ncall chain:\nnfsd4_delegreturn --\u003e destroy_delegation --\u003e destroy_unhashed_deleg --\u003e\nnfs4_unlock_deleg_lease --\u003e kernel_setlease --\u003e generic_delete_lease\nThe corresponding sc_count reference will be released after this\ndisassociation.\n\nSince nfsd_break_one_deleg executes while holding the flc_lock, the\ndisassociation process becomes blocked when attempting to acquire flc_lock\nin generic_delete_lease. This means:\n1) sc_count in nfsd_break_one_deleg will not be decremented to 0;\n2) The nfs4_put_stid called by nfsd_break_one_deleg will not attempt to\nacquire cl_lock;\n3) Consequently, no deadlock condition is created.\n\nGiven that sc_count in nfsd_break_one_deleg remains non-zero, we can\nsafely perform refcount_dec on sc_count directly. This approach\neffectively avoids triggering deadlock warnings.",
"id": "GHSA-qwrm-23w5-g55v",
"modified": "2025-11-12T21:31:02Z",
"published": "2025-05-09T09:33:20Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-37871"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/14985d66b9b99c12995dd99d1c6c8dec4114c2a5"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7d192e27a431026c58d60edf66dc6cd98d0c01fc"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a1d14d931bf700c1025db8c46d6731aa5cf440f9"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a70832d3555987035fc430ccd703acd89393eadb"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a7fce086f6ca84db409b9d58493ea77c1978897c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b9bbe8f9d5663311d06667ce36d6ed255ead1a26"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ba903539fff745d592d893c71b30e5e268a95413"
},
{
"type": "WEB",
"url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html"
},
{
"type": "WEB",
"url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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