CVE-2025-38338 (GCVE-0-2025-38338)
Vulnerability from cvelistv5 – Published: 2025-07-10 08:15 – Updated: 2026-05-11 21:26
VLAI
EPSS
VEX
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:
<TASK>
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
never happens because nobody is really holding the folio lock.
Severity
7.8 (High)
Assigner
References
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
000dbe0bec058cbf2ca9e156e4a5584f5158b0f9 , < 14f5549ad163be2c018abc1bb38370fff617a243
(git)
Affected: 000dbe0bec058cbf2ca9e156e4a5584f5158b0f9 , < 5bf0b9eeb0174686f22c2e5b8fb9f47ad25da6f5 (git) Affected: 000dbe0bec058cbf2ca9e156e4a5584f5158b0f9 , < 1e93b61d3eaa14bfebcc2716ac09d43f3845d420 (git) Affected: 000dbe0bec058cbf2ca9e156e4a5584f5158b0f9 , < 4c10fa44bc5f700e2ea21de2fbae520ba21f19d9 (git) |
guessed | |
| Linux | Linux |
Affected:
6.4
Unaffected: 0 , < 6.4 (semver) Unaffected: 6.6.95 , ≤ 6.6.* (semver) Unaffected: 6.12.35 , ≤ 6.12.* (semver) Unaffected: 6.15.4 , ≤ 6.15.* (semver) Unaffected: 6.16 , ≤ * (original_commit_for_fix) |
guessed |
{
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}
]
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"cpeApplicability": [
{
"nodes": [
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},
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},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.15.4",
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"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"descriptions": [
{
"lang": "en",
"value": "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 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 \u003cTASK\u003e\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."
}
],
"providerMetadata": {
"dateUpdated": "2026-05-11T21:26:03.883Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"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"
}
],
"title": "fs/nfs/read: fix double-unlock bug in nfs_return_empty_folio()",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2025-38338",
"datePublished": "2025-07-10T08:15:09.022Z",
"dateReserved": "2025-04-16T04:51:24.005Z",
"dateUpdated": "2026-05-11T21:26:03.883Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2025-38338",
"date": "2026-09-16",
"epss": "0.00162",
"percentile": "0.05852"
},
"microsoft_vex": {
"current_release_date": "2026-02-18T14:59:45.000Z",
"cve": "CVE-2025-38338",
"id": "msrc_CVE-2025-38338",
"initial_release_date": "2025-07-02T00:00:00.000Z",
"product_status:fixed": "2",
"product_status:known_affected": "2",
"source": "Microsoft CSAF VEX",
"status": "final",
"title": "fs/nfs/read: fix double-unlock bug in nfs_return_empty_folio()",
"url": "https://msrc.microsoft.com/csaf/vex/2025/msrc_cve-2025-38338.json",
"version": "2"
},
"nvd": "{\"cve\":{\"id\":\"CVE-2025-38338\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-07-10T09:15:28.510\",\"lastModified\":\"2026-06-17T09:16:39.273\",\"vulnStatus\":\"Analyzed\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"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 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 \u003cTASK\u003e\\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.\"},{\"lang\":\"es\",\"value\":\"En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: fs/nfs/read: corrige error de doble desbloqueo en nfs_return_empty_folio() En ocasiones, cuando se le\u00eda un archivo mientras otro cliente NFS lo estaba truncando, el kernel pod\u00eda bloquearse porque se llamaba a folio_unlock() dos veces y la segunda llamada XOR devolver\u00eda el indicador `PG_locked`. La mayor\u00eda de las veces (dependiendo del momento del truncamiento), nadie nota el problema porque folio_unlock() se llama tres veces, lo que desactiva `PG_locked`: 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 El problema es que nfs_read_add_folio() no debe desbloquear el folio si fscache est\u00e1 habilitado, y falta una comprobaci\u00f3n nfs_netfs_folio_unlock() en nfs_return_empty_folio(). En raras ocasiones, esto genera una advertencia en netfs_read_collection(): ------------[ cortar aqu\u00ed ]------------ R=0000031c: el folio 10 no est\u00e1 bloqueado ADVERTENCIA: CPU: 0 PID: 29 en fs/netfs/read_collect.c:133 netfs_read_collection+0x7c0/0xf00 [...] Cola de trabajo: events_unbound netfs_read_collection_worker RIP: 0010:netfs_read_collection+0x7c0/0xf00 [...] Rastreo de llamadas: netfs_read_collection_worker+0x67/0x80 process_one_work+0x12e/0x2c0worker_thread+0x295/0x3a0 Sin embargo, la mayor\u00eda de las veces, los procesos simplemente se quedan atascados para siempre en folio_wait_bit_common(), esperando que `PG_locked` desaparezca, lo que nunca sucede porque nadie est\u00e1 realmente reteniendo el cerradura de folio. \"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"fs/nfs/read.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"000dbe0bec058cbf2ca9e156e4a5584f5158b0f9\",\"lessThan\":\"14f5549ad163be2c018abc1bb38370fff617a243\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"000dbe0bec058cbf2ca9e156e4a5584f5158b0f9\",\"lessThan\":\"5bf0b9eeb0174686f22c2e5b8fb9f47ad25da6f5\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"000dbe0bec058cbf2ca9e156e4a5584f5158b0f9\",\"lessThan\":\"1e93b61d3eaa14bfebcc2716ac09d43f3845d420\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"000dbe0bec058cbf2ca9e156e4a5584f5158b0f9\",\"lessThan\":\"4c10fa44bc5f700e2ea21de2fbae520ba21f19d9\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"fs/nfs/read.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"6.4\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"6.4\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.6.95\",\"lessThanOrEqual\":\"6.6.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.35\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.15.4\",\"lessThanOrEqual\":\"6.15.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.16\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":7.8,\"baseSeverity\":\"HIGH\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":5.9}]},\"weaknesses\":[{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-415\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.4\",\"versionEndExcluding\":\"6.6.95\",\"matchCriteriaId\":\"F17A70D5-5B72-4411-9C16-98EF57D0C931\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.7\",\"versionEndExcluding\":\"6.12.35\",\"matchCriteriaId\":\"E569FD34-0076-4428-BE17-EECCF867611C\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.13\",\"versionEndExcluding\":\"6.15.4\",\"matchCriteriaId\":\"DFD174C5-1AA2-4671-BDDC-1A9FCC753655\"}]}]}],\"references\":[{\"url\":\"https://git.kernel.org/stable/c/14f5549ad163be2c018abc1bb38370fff617a243\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/1e93b61d3eaa14bfebcc2716ac09d43f3845d420\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/4c10fa44bc5f700e2ea21de2fbae520ba21f19d9\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/5bf0b9eeb0174686f22c2e5b8fb9f47ad25da6f5\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]}]}}",
"redhat_vex": {
"aggregate_severity": "Moderate",
"current_release_date": "2026-06-30T01:04:24+00:00",
"cve": "CVE-2025-38338",
"id": "CVE-2025-38338",
"initial_release_date": "2025-07-10T00:00:00+00:00",
"product_status:known_affected": "198",
"product_status:known_not_affected": "76",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "kernel: fs/nfs/read: fix double-unlock bug in nfs_return_empty_folio()",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-38338.json",
"version": "3"
},
"suse_vex": {
"aggregate_severity": "moderate",
"current_release_date": "2026-08-30T01:55:24Z",
"cve": "CVE-2025-38338",
"id": "CVE-2025-38338",
"initial_release_date": "2025-07-10T23:22:15Z",
"product_status:first_fixed": "2",
"product_status:known_affected": "394",
"product_status:known_not_affected": "442",
"product_status:recommended": "472",
"source": "SUSE CSAF VEX",
"status": "interim",
"title": "SUSE CVE CVE-2025-38338",
"url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2025-38338.json",
"version": "43"
}
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
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They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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