{"id":"CVE-2025-38338","title":"fs/nfs/read: fix double-unlock bug in nfs_return_empty_folio()","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nfs/nfs/read: fix double-unlock bug in nfs_return_empty_folio()\n\nSometimes, when a file was read while it was being truncated by\nanother NFS client, the kernel could dea…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 000dbe0bec058cbf2ca9e156e4a5584f5158b0f9 < 14f5549ad163be2c018abc1bb38370fff617a243","Linux >= 000dbe0bec058cbf2ca9e156e4a5584f5158b0f9 < 5bf0b9eeb0174686f22c2e5b8fb9f47ad25da6f5","Linux >= 000dbe0bec058cbf2ca9e156e4a5584f5158b0f9 < 1e93b61d3eaa14bfebcc2716ac09d43f3845d420","Linux >= 000dbe0bec058cbf2ca9e156e4a5584f5158b0f9 < 4c10fa44bc5f700e2ea21de2fbae520ba21f19d9","Linux 6.4"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-11-05T20:55:00.358504Z"},"published":"2025-07-10","updated":"2026-11-05","sourceUpdated":"2026-11-05T21:02:34.128Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2025-38338","references":[{"url":"https://git.kernel.org/stable/c/14f5549ad163be2c018abc1bb38370fff617a243"},{"url":"https://git.kernel.org/stable/c/5bf0b9eeb0174686f22c2e5b8fb9f47ad25da6f5"},{"url":"https://git.kernel.org/stable/c/1e93b61d3eaa14bfebcc2716ac09d43f3845d420"},{"url":"https://git.kernel.org/stable/c/4c10fa44bc5f700e2ea21de2fbae520ba21f19d9"}],"tags":["cve.org"],"epss":0.00185,"epssPercentile":0.08162,"ingestedAt":"2026-11-05T22:38:31.960Z","slug":"CVE-2025-38338","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nfs/nfs/read: fix double-unlock bug in nfs_return_empty_folio()\n\nSometimes, when a file was read while it was being truncated by\nanother NFS client, the kernel could deadlock because folio_unlock()\nwas called twice, and the second call would XOR back the `PG_locked`\nflag.\n\nMost of the time (depending on the timing of the truncation), nobody\nnotices the problem because folio_unlock() gets called three times,\nwhich flips `PG_locked` back off:\n\n 1. vfs_read, nfs_read_folio, ... nfs_read_add_folio,\n    nfs_return_empty_folio\n 2. vfs_read, nfs_read_folio, ... netfs_read_collection,\n    netfs_unlock_abandoned_read_pages\n 3. vfs_read, ... nfs_do_read_folio, nfs_read_add_folio,\n    nfs_return_empty_folio\n\nThe problem is that nfs_read_add_folio() is not supposed to unlock the\nfolio if fscache is enabled, and a nfs_netfs_folio_unlock() check is\nmissing in nfs_return_empty_folio().\n\nRarely this leads to a warning in netfs_read_collection():\n\n ------------[ cut here ]------------\n R=0000031c: folio 10 is not locked\n WARNING: CPU: 0 PID: 29 at fs/netfs/read_collect.c:133 netfs_read_collection+0x7c0/0xf00\n [...]\n Workqueue: events_unbound netfs_read_collection_worker\n RIP: 0010:netfs_read_collection+0x7c0/0xf00\n [...]\n Call Trace:\n  <TASK>\n  netfs_read_collection_worker+0x67/0x80\n  process_one_work+0x12e/0x2c0\n  worker_thread+0x295/0x3a0\n\nMost of the time, however, processes just get stuck forever in\nfolio_wait_bit_common(), waiting for `PG_locked` to disappear, which\nnever happens because nobody is really holding the folio lock.\n\n## Affected\n\n- `Linux >= 000dbe0bec058cbf2ca9e156e4a5584f5158b0f9 < 14f5549ad163be2c018abc1bb38370fff617a243`\n- `Linux >= 000dbe0bec058cbf2ca9e156e4a5584f5158b0f9 < 5bf0b9eeb0174686f22c2e5b8fb9f47ad25da6f5`\n- `Linux >= 000dbe0bec058cbf2ca9e156e4a5584f5158b0f9 < 1e93b61d3eaa14bfebcc2716ac09d43f3845d420`\n- `Linux >= 000dbe0bec058cbf2ca9e156e4a5584f5158b0f9 < 4c10fa44bc5f700e2ea21de2fbae520ba21f19d9`\n- `Linux 6.4`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}