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GHSA-H8FH-268C-FHWM

Vulnerability from github – Published: 2025-01-19 12:31 – Updated: 2025-10-16 21:31

Details

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

netfs: Fix kernel async DIO

Netfslib needs to be able to handle kernel-initiated asynchronous DIO that is supplied with a bio_vec[] array. Currently, because of the async flag, this gets passed to netfs_extract_user_iter() which throws a warning and fails because it only handles IOVEC and UBUF iterators. This can be triggered through a combination of cifs and a loopback blockdev with something like:

    mount //my/cifs/share /foo
    dd if=/dev/zero of=/foo/m0 bs=4K count=1K
    losetup --sector-size 4096 --direct-io=on /dev/loop2046 /foo/m0
    echo hello >/dev/loop2046

This causes the following to appear in syslog:

    WARNING: CPU: 2 PID: 109 at fs/netfs/iterator.c:50 netfs_extract_user_iter+0x170/0x250 [netfs]

and the write to fail.

Fix this by removing the check in netfs_unbuffered_write_iter_locked() that causes async kernel DIO writes to be handled as userspace writes. Note that this change relies on the kernel caller maintaining the existence of the bio_vec array (or kvec[] or folio_queue) until the op is complete.

Severity

5.5 (Medium)


                  
                    CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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{
  "affected": [],
  "aliases": [
    "CVE-2025-21643"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-01-19T11:15:09Z",
    "severity": "MODERATE"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfs: Fix kernel async DIO\n\nNetfslib needs to be able to handle kernel-initiated asynchronous DIO that\nis supplied with a bio_vec[] array.  Currently, because of the async flag,\nthis gets passed to netfs_extract_user_iter() which throws a warning and\nfails because it only handles IOVEC and UBUF iterators.  This can be\ntriggered through a combination of cifs and a loopback blockdev with\nsomething like:\n\n        mount //my/cifs/share /foo\n        dd if=/dev/zero of=/foo/m0 bs=4K count=1K\n        losetup --sector-size 4096 --direct-io=on /dev/loop2046 /foo/m0\n        echo hello \u003e/dev/loop2046\n\nThis causes the following to appear in syslog:\n\n        WARNING: CPU: 2 PID: 109 at fs/netfs/iterator.c:50 netfs_extract_user_iter+0x170/0x250 [netfs]\n\nand the write to fail.\n\nFix this by removing the check in netfs_unbuffered_write_iter_locked() that\ncauses async kernel DIO writes to be handled as userspace writes.  Note\nthat this change relies on the kernel caller maintaining the existence of\nthe bio_vec array (or kvec[] or folio_queue) until the op is complete.",
  "id": "GHSA-h8fh-268c-fhwm",
  "modified": "2025-10-16T21:31:14Z",
  "published": "2025-01-19T12:31:25Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-21643"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3f6bc9e3ab9b127171d39f9ac6eca1abb693b731"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/9f3a265836844eda30bf34c2584b8011fd4f0f49"
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  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2025-21643 (GCVE-0-2025-21643)

Vulnerability from cvelistv5 – Published: 2025-01-19 10:17 – Updated: 2026-05-11 21:03

Title

netfs: Fix kernel async DIO

Summary

In the Linux kernel, the following vulnerability has been resolved: netfs: Fix kernel async DIO Netfslib needs to be able to handle kernel-initiated asynchronous DIO that is supplied with a bio_vec[] array. Currently, because of the async flag, this gets passed to netfs_extract_user_iter() which throws a warning and fails because it only handles IOVEC and UBUF iterators. This can be triggered through a combination of cifs and a loopback blockdev with something like: mount //my/cifs/share /foo dd if=/dev/zero of=/foo/m0 bs=4K count=1K losetup --sector-size 4096 --direct-io=on /dev/loop2046 /foo/m0 echo hello >/dev/loop2046 This causes the following to appear in syslog: WARNING: CPU: 2 PID: 109 at fs/netfs/iterator.c:50 netfs_extract_user_iter+0x170/0x250 [netfs] and the write to fail. Fix this by removing the check in netfs_unbuffered_write_iter_locked() that causes async kernel DIO writes to be handled as userspace writes. Note that this change relies on the kernel caller maintaining the existence of the bio_vec array (or kvec[] or folio_queue) until the op is complete.

Severity

No CVSS data available.

Assigner

Linux CNA under the mitre root

CNA scorecard D 53/100 over 6666 records in the last 180 days details

References

2 references

URL	Tags
https://git.kernel.org/stable/c/9f3a265836844eda3…
https://git.kernel.org/stable/c/3f6bc9e3ab9b12717…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 153a9961b551101cd38e94e26cd92fbfd198b19b , < 9f3a265836844eda30bf34c2584b8011fd4f0f49 (git) Affected: 153a9961b551101cd38e94e26cd92fbfd198b19b , < 3f6bc9e3ab9b127171d39f9ac6eca1abb693b731 (git)
Linux	Linux	Affected: 6.8 Unaffected: 0 , < 6.8 (semver) Unaffected: 6.12.10 , ≤ 6.12.* (semver) Unaffected: 6.13 , ≤ * (original_commit_for_fix)

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JSON

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          "programFiles": [
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              "cpeMatch": [
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                },
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    "dateReserved": "2024-12-29T08:45:45.727Z",
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Sightings

Author	Source	Type	Date	Other

Nomenclature

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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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