CVE-2026-89835 (GCVE-0-2026-89835)

Vulnerability from cvelistv5 – Published: 2026-09-16 10:31 – Updated: 2026-09-16 10:31
VLAI
Title
f2fs: avoid NULL checkpoint thread access in sysfs
Summary
In the Linux kernel, the following vulnerability has been resolved: f2fs: avoid NULL checkpoint thread access in sysfs checkpoint_merge can be enabled even when no checkpoint merge thread is running. A read-only mount is one case: f2fs does not start f2fs_issue_ckpt there, but ckpt_thread_ioprio is still writable through sysfs. The ckpt_thread_ioprio store path updates the saved ioprio value and, when checkpoint_merge is enabled, calls set_task_ioprio() for the checkpoint thread. If cprc->f2fs_issue_ckpt is NULL, that dereferences a NULL task pointer. Protect ckpt_thread_ioprio sysfs writes with s_umount as well, so the checkpoint thread cannot disappear under the store path while updating its ioprio.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: e65920661708b7c0f3db45c9cd5d0095034ee37f , < a6573f3ffc19542de9ebc1a2b1f930fd48ba538c (git)
Affected: e65920661708b7c0f3db45c9cd5d0095034ee37f , < aefcec3bebdeed2bff444378122300763325ba23 (git)
Affected: e65920661708b7c0f3db45c9cd5d0095034ee37f , < 8f3b99c50dd0da1777994ce7c7e60d39b9f60f4b (git)
Affected: e65920661708b7c0f3db45c9cd5d0095034ee37f , < 5cb33b00c8fbb6e8f1fa3d281c3036d5f7c7c41f (git)
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Linux Linux Affected: 5.12
Unaffected: 0 , < 5.12 (semver)
Unaffected: 6.12.110 , ≤ 6.12.* (semver)
Unaffected: 6.18.51 , ≤ 6.18.* (semver)
Unaffected: 7.2.5 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)
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{
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          "product": "Linux",
          "programFiles": [
            "fs/f2fs/sysfs.c"
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: avoid NULL checkpoint thread access in sysfs\n\ncheckpoint_merge can be enabled even when no checkpoint merge thread is\nrunning. A read-only mount is one case: f2fs does not start\nf2fs_issue_ckpt there, but ckpt_thread_ioprio is still writable through\nsysfs.\n\nThe ckpt_thread_ioprio store path updates the saved ioprio value and,\nwhen checkpoint_merge is enabled, calls set_task_ioprio() for the\ncheckpoint thread. If cprc-\u003ef2fs_issue_ckpt is NULL, that dereferences a\nNULL task pointer.\n\nProtect ckpt_thread_ioprio sysfs writes with s_umount as well, so the\ncheckpoint thread cannot disappear under the store path while updating\nits ioprio."
        }
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        "shortName": "Linux"
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    "cveId": "CVE-2026-89835",
    "datePublished": "2026-09-16T10:31:08.636Z",
    "dateReserved": "2026-09-11T19:38:34.769Z",
    "dateUpdated": "2026-09-16T10:31:08.636Z",
    "state": "PUBLISHED"
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      "date": "2026-09-25",
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        "descriptions": [
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: avoid NULL checkpoint thread access in sysfs\n\ncheckpoint_merge can be enabled even when no checkpoint merge thread is\nrunning. A read-only mount is one case: f2fs does not start\nf2fs_issue_ckpt there, but ckpt_thread_ioprio is still writable through\nsysfs.\n\nThe ckpt_thread_ioprio store path updates the saved ioprio value and,\nwhen checkpoint_merge is enabled, calls set_task_ioprio() for the\ncheckpoint thread. If cprc-\u003ef2fs_issue_ckpt is NULL, that dereferences a\nNULL task pointer.\n\nProtect ckpt_thread_ioprio sysfs writes with s_umount as well, so the\ncheckpoint thread cannot disappear under the store path while updating\nits ioprio."
          }
        ],
        "id": "CVE-2026-89835",
        "lastModified": "2026-09-16T11:16:50.290",
        "metrics": {},
        "published": "2026-09-16T11:16:50.290",
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
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}



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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

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Nomenclature

  • 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.
  • 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.



Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.