GHSA-QV85-292C-84HH

Vulnerability from github – Published: 2026-09-11 21:31 – Updated: 2026-10-30 15:33
VLAI
Details

In 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.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Show details on source website
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{
  "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": "2026-10-30T15:33:24Z",
  "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/18847cbf5900f5c6c55bef5a6f7a34a1918d1181"
    },
    {
      "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"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/bdf5a0f88d21239d8f9f7519b87359ba95fd045c"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e301c5cdb0dc2c4aeffc0c055ea15615d9c51fdc"
    }
  ],
  "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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