fs/nfs/read: fix double-unlock bug in nfs_return_empty_folio()

{
  "id": "eed860bc73f39669e376f55683e288d7ab508064eb1e9eadaed3a143ee8e06b5",
  "url": "https://osv.dev/vulnerability/CVE-2025-38338",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "fs/nfs/read: fix double-unlock bug in nfs_return_empty_folio()",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: fs/nfs/read: fix double-unlock bug in nfs_return_empty_folio() Sometimes, when a file was read while it was being truncated by another NFS client, the kernel could deadlock because folio_unlock() was called twice, and the second call would XOR back the `PG_locked` flag. Most of the time (depending on the timing of the truncation), nobody notices the problem because folio_unlock() gets called three times, which flips `PG_locked` back off: 1. vfs_read, nfs_read_folio, ... nfs_read_add_folio, nfs_return_empty_folio 2. vfs_read, nfs_read_folio, ... netfs_read_collection, netfs_unlock_abandoned_read_pages 3. vfs_read, ... nfs_do_read_folio, nfs_read_add_folio, nfs_return_empty_folio The problem is that nfs_read_add_folio() is not supposed to unlock the folio if fscache is enabled, and a nfs_netfs_folio_unlock() check is missing in nfs_return_empty_folio(). Rarely this leads to a warning in netfs_read_collection(): ------------[ cut here ]------------ R=0000031c: folio 10 is not locked WARNING: CPU: 0 PID: 29 at fs/netfs/read_collect.c:133 netfs_read_collection+0x7c0/0xf00 [...] Workqueue: events_unbound netfs_read_collection_worker RIP: 0010:netfs_read_collection+0x7c0/0xf00 [...] Call Trace: netfs_read_collection_worker+0x67/0x80 process_one_work+0x12e/0x2c0 worker_thread+0x295/0x3a0 Most of the time, however, processes just get stuck forever in folio_wait_bit_common(), waiting for `PG_locked` to disappear, which",
    "evidence": "osv:CVE-2025-38338",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.6.95",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.35",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.15.4",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2025-38338",
      "aliases": [
        "CVE-2025-38338"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
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                  "introduced": "000dbe0bec058cbf2ca9e156e4a5584f5158b0f9"
                },
                {
                  "fixed": "14f5549ad163be2c018abc1bb38370fff617a243"
                },
                {
                  "fixed": "5bf0b9eeb0174686f22c2e5b8fb9f47ad25da6f5"
                },
                {
                  "fixed": "1e93b61d3eaa14bfebcc2716ac09d43f3845d420"
                },
                {
                  "fixed": "4c10fa44bc5f700e2ea21de2fbae520ba21f19d9"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-38338.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.4.0"
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                {
                  "fixed": "6.6.95"
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              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.7.0"
                },
                {
                  "fixed": "6.12.35"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.15.4"
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              ]
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          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-38338.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:37.486929478Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/14f5549ad163be2c018abc1bb38370fff617a243",
        "https://git.kernel.org/stable/c/1e93b61d3eaa14bfebcc2716ac09d43f3845d420",
        "https://git.kernel.org/stable/c/4c10fa44bc5f700e2ea21de2fbae520ba21f19d9",
        "https://git.kernel.org/stable/c/5bf0b9eeb0174686f22c2e5b8fb9f47ad25da6f5",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/38xxx/CVE-2025-38338.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-38338",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/38xxx/CVE-2025-38338.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2025-38338",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 504563,
  "published_at": "2025-07-10T08:15:09.022+00:00"
}