CVE-2026-31404 (GCVE-0-2026-31404)

Vulnerability from cvelistv5 – Published: 2026-04-03 15:16 – Updated: 2026-05-11 22:08
VLAI
Title
NFSD: Defer sub-object cleanup in export put callbacks
Summary
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>
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: c224edca7af028828e2ad866b61d731b5e72b46d , < 2829e80d29b627886d12b5ea40856d56b516e67d (git)
Affected: c224edca7af028828e2ad866b61d731b5e72b46d , < f5ab1bec5fa18731e0b1b1e60c9a68667ac73ea2 (git)
Affected: c224edca7af028828e2ad866b61d731b5e72b46d , < 48db892356d6cb80f6942885545de4a6dd8d2a29 (git)
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Linux Linux Affected: 6.14
Unaffected: 0 , < 6.14 (semver)
Unaffected: 6.18.20 , ≤ 6.18.* (semver)
Unaffected: 6.19.10 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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          "value": "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"
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    "datePublished": "2026-04-03T15:16:07.207Z",
    "dateReserved": "2026-03-09T15:48:24.086Z",
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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\"},{\"lang\":\"es\",\"value\":\"En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\\n\\nNFSD: Aplazar la limpieza de subobjetos en las retrollamadas de liberaci\u00f3n de exportaci\u00f3n\\n\\nsvc_export_put() llama a path_put() y auth_domain_put() inmediatamente cuando la \u00faltima referencia se elimina, antes del per\u00edodo de gracia de RCU. Los lectores de RCU en e_show() y c_show() acceden tanto a ex_path (a trav\u00e9s de seq_path/d_path) como a ex_client -\u003e name (a trav\u00e9s de seq_escape) sin mantener una referencia. Si cache_clean elimina la entrada y elimina la \u00faltima referencia concurrentemente, los subobjetos son liberados mientras a\u00fan est\u00e1n en uso, produciendo una desreferenciaci\u00f3n de puntero NULL en d_path.\\n\\nEl Commit 2530766492ec (\u0027nfsd: corregir UAF al acceder a ex_uuid o ex_stats\u0027) movi\u00f3 kfree de ex_uuid y ex_stats a la retrollamada call_rcu, pero dej\u00f3 path_put() y auth_domain_put() ejecut\u00e1ndose antes del per\u00edodo de gracia porque ambos pueden entrar en suspensi\u00f3n y las retrollamadas call_rcu se ejecutan en contexto de softirq.\\n\\nReemplazar call_rcu/kfree_rcu con queue_rcu_work(), lo que aplaza la retrollamada hasta despu\u00e9s del per\u00edodo de gracia de RCU y la ejecuta en contexto de proceso donde se permite la suspensi\u00f3n. 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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-06-30T11:46:46+00:00",
      "cve": "CVE-2026-31404",
      "id": "CVE-2026-31404",
      "initial_release_date": "2026-04-03T00:00:00+00:00",
      "product_status:known_affected": "198",
      "product_status:known_not_affected": "76",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: NFSD: Defer sub-object cleanup in export put callbacks",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-31404.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-07-15T05:23:16Z",
      "cve": "CVE-2026-31404",
      "id": "CVE-2026-31404",
      "initial_release_date": "2026-04-03T23:25:41Z",
      "product_status:known_affected": "452",
      "product_status:known_not_affected": "184",
      "product_status:recommended": "123",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-31404",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-31404.json",
      "version": "14"
    }
  }
}



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Sightings

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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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