GHSA-M9X4-X7J5-6V8X

Vulnerability from github – Published: 2026-04-03 18:31 – Updated: 2026-04-03 18:31
VLAI?
Details

In the Linux kernel, the following vulnerability has been resolved:

NFSD: Defer sub-object cleanup in export put callbacks

svc_export_put() calls path_put() and auth_domain_put() immediately when the last reference drops, before the RCU grace period. RCU readers in e_show() and c_show() access both ex_path (via seq_path/d_path) and ex_client->name (via seq_escape) without holding a reference. If cache_clean removes the entry and drops the last reference concurrently, the sub-objects are freed while still in use, producing a NULL pointer dereference in d_path.

Commit 2530766492ec ("nfsd: fix UAF when access ex_uuid or ex_stats") moved kfree of ex_uuid and ex_stats into the call_rcu callback, but left path_put() and auth_domain_put() running before the grace period because both may sleep and call_rcu callbacks execute in softirq context.

Replace call_rcu/kfree_rcu with queue_rcu_work(), which defers the callback until after the RCU grace period and executes it in process context where sleeping is permitted. This allows path_put() and auth_domain_put() to be moved into the deferred callback alongside the other resource releases. Apply the same fix to expkey_put(), which has the identical pattern with ek_path and ek_client.

A dedicated workqueue scopes the shutdown drain to only NFSD export release work items; flushing the shared system_unbound_wq would stall on unrelated work from other subsystems. nfsd_export_shutdown() uses rcu_barrier() followed by flush_workqueue() to ensure all deferred release callbacks complete before the export caches are destroyed.

Reviwed-by: Jeff Layton jlayton@kernel.org

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{
  "affected": [],
  "aliases": [
    "CVE-2026-31404"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-04-03T16:16:39Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: Defer sub-object cleanup in export put callbacks\n\nsvc_export_put() calls path_put() and auth_domain_put() immediately\nwhen the last reference drops, before the RCU grace period. RCU\nreaders in e_show() and c_show() access both ex_path (via\nseq_path/d_path) and ex_client-\u003ename (via seq_escape) without\nholding a reference. If cache_clean removes the entry and drops the\nlast reference concurrently, the sub-objects are freed while still\nin use, producing a NULL pointer dereference in d_path.\n\nCommit 2530766492ec (\"nfsd: fix UAF when access ex_uuid or\nex_stats\") moved kfree of ex_uuid and ex_stats into the\ncall_rcu callback, but left path_put() and auth_domain_put() running\nbefore the grace period because both may sleep and call_rcu\ncallbacks execute in softirq context.\n\nReplace call_rcu/kfree_rcu with queue_rcu_work(), which defers the\ncallback until after the RCU grace period and executes it in process\ncontext where sleeping is permitted. This allows path_put() and\nauth_domain_put() to be moved into the deferred callback alongside\nthe other resource releases. Apply the same fix to expkey_put(),\nwhich has the identical pattern with ek_path and ek_client.\n\nA dedicated workqueue scopes the shutdown drain to only NFSD\nexport release work items; flushing the shared\nsystem_unbound_wq would stall on unrelated work from other\nsubsystems. nfsd_export_shutdown() uses rcu_barrier() followed\nby flush_workqueue() to ensure all deferred release callbacks\ncomplete before the export caches are destroyed.\n\nReviwed-by: Jeff Layton \u003cjlayton@kernel.org\u003e",
  "id": "GHSA-m9x4-x7j5-6v8x",
  "modified": "2026-04-03T18:31:23Z",
  "published": "2026-04-03T18:31:23Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-31404"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2829e80d29b627886d12b5ea40856d56b516e67d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/48db892356d6cb80f6942885545de4a6dd8d2a29"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f5ab1bec5fa18731e0b1b1e60c9a68667ac73ea2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}


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