GHSA-QV85-292C-84HH
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: release path refs on follow_down() error
nfsd_cross_mnt() initializes a local struct path with mntget() and dget() before calling follow_down(). On a negative return the error arm jumps to out without releasing those references:
err = follow_down(&path, follow_flags);
if (err < 0)
goto out;
follow_down() never drops the caller's entry-time refs on any error sub-case; for example a pre-cross d_manage() failure leaves path untouched, so the mntget()/dget() taken on entry survive the call.
Every other early-exit arm in nfsd_cross_mnt() (other-namespace return, IS_ERR(exp2), and the success tail after the swap) already calls path_put(&path); the err < 0 arm is the lone omission. The leak inflates mnt_count and d_count on each failed cross-mount, blocking umount and pinning dentries against the shrinker, and is reachable by any authenticated NFS client through nfsd_lookup_dentry or the NFSv4 READDIR encode path.
Fix by calling path_put(&path) before the goto out in the err < 0 arm so the entry-time refs are released on all follow_down() error returns.
{
"affected": [],
"aliases": [
"CVE-2026-89707"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-11T20:19:58Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: release path refs on follow_down() error\n\nnfsd_cross_mnt() initializes a local struct path with mntget() and\ndget() before calling follow_down(). On a negative return the error\narm jumps to out without releasing those references:\n\n err = follow_down(\u0026path, follow_flags);\n if (err \u003c 0)\n goto out;\n\nfollow_down() never drops the caller\u0027s entry-time refs on any error\nsub-case; for example a pre-cross d_manage() failure leaves path\nuntouched, so the mntget()/dget() taken on entry survive the call.\n\nEvery other early-exit arm in nfsd_cross_mnt() (other-namespace\nreturn, IS_ERR(exp2), and the success tail after the swap) already\ncalls path_put(\u0026path); the err \u003c 0 arm is the lone omission. The\nleak inflates mnt_count and d_count on each failed cross-mount,\nblocking umount and pinning dentries against the shrinker, and is\nreachable by any authenticated NFS client through nfsd_lookup_dentry\nor the NFSv4 READDIR encode path.\n\nFix by calling path_put(\u0026path) before the goto out in the err \u003c 0\narm so the entry-time refs are released on all follow_down() error\nreturns.",
"id": "GHSA-qv85-292c-84hh",
"modified": "2026-09-14T15:32:34Z",
"published": "2026-09-11T21:31:37Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89707"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/085cfde7c2186acaad103f02d2c25435ad5224e9"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/194316df81263519156ebe714c4a286bee00e5be"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2bc4343308d85ee4e0dd3877b384306c96f114c2"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/467d56fd3ff57447a790c6dc3ede2d02a947d224"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/6cba08dc1922140d260cfeb30bbda4ee1bf869d8"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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