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GHSA-4XRV-JF38-655F

Vulnerability from github – Published: 2026-09-25 12:31 – Updated: 2026-09-25 12:31

Details

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

btrfs: zstd: fix lost wakeup when waiting for a workspace

A writer can sleep forever in zstd_get_workspace() even though a workspace is free. When zstd_alloc_workspace() fails, the task is queued on zwsm->wait and schedules unconditionally, never re-testing the pool. zstd_put_workspace() publishes the workspace and then calls cond_wake_up(), which only wakes when a sleeper is already visible, so a workspace returned between the failed allocation and prepare_to_wait() wakes nobody. The window is wide: zstd_alloc_workspace() goes through kvmalloc() and may enter reclaim.

Only a max level workspace triggers the wakeup and one is deliberately kept allocated as the fallback every waiter waits for, so once its wakeup is lost the writer stays in TASK_UNINTERRUPTIBLE until some other task happens to return one. Re-check the pool after prepare_to_wait() has published the waiter, and use the workspace if one turned up.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-98079"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-25T11:17:37Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: zstd: fix lost wakeup when waiting for a workspace\n\nA writer can sleep forever in zstd_get_workspace() even though a workspace\nis free.  When zstd_alloc_workspace() fails, the task is queued on\nzwsm-\u003ewait and schedules unconditionally, never re-testing the pool.\nzstd_put_workspace() publishes the workspace and then calls cond_wake_up(),\nwhich only wakes when a sleeper is already visible, so a workspace returned\nbetween the failed allocation and prepare_to_wait() wakes nobody.  The\nwindow is wide: zstd_alloc_workspace() goes through kvmalloc() and may\nenter reclaim.\n\nOnly a max level workspace triggers the wakeup and one is deliberately kept\nallocated as the fallback every waiter waits for, so once its wakeup is\nlost the writer stays in TASK_UNINTERRUPTIBLE until some other task happens\nto return one.  Re-check the pool after prepare_to_wait() has published the\nwaiter, and use the workspace if one turned up.",
  "id": "GHSA-4xrv-jf38-655f",
  "modified": "2026-09-25T12:31:36Z",
  "published": "2026-09-25T12:31:36Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98079"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0de9f31d447ae71ab08c7850a321682f8d2907c3"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2acb9f3d1cc8f65dc81ed55e238cbf8e5b60bff7"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d8f57049521948df5f50797141472fbbed3b0723"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

CVE-2026-98079 (GCVE-0-2026-98079)

Vulnerability from cvelistv5 – Published: 2026-09-25 10:24 – Updated: 2026-09-25 10:24

Title

btrfs: zstd: fix lost wakeup when waiting for a workspace

Summary

In the Linux kernel, the following vulnerability has been resolved: btrfs: zstd: fix lost wakeup when waiting for a workspace A writer can sleep forever in zstd_get_workspace() even though a workspace is free. When zstd_alloc_workspace() fails, the task is queued on zwsm->wait and schedules unconditionally, never re-testing the pool. zstd_put_workspace() publishes the workspace and then calls cond_wake_up(), which only wakes when a sleeper is already visible, so a workspace returned between the failed allocation and prepare_to_wait() wakes nobody. The window is wide: zstd_alloc_workspace() goes through kvmalloc() and may enter reclaim. Only a max level workspace triggers the wakeup and one is deliberately kept allocated as the fallback every waiter waits for, so once its wakeup is lost the writer stays in TASK_UNINTERRUPTIBLE until some other task happens to return one. Re-check the pool after prepare_to_wait() has published the waiter, and use the workspace if one turned up.

Severity

No CVSS data available.

Assigner

Linux mitre root

References

3 references

URL	Tags
https://git.kernel.org/stable/c/d8f57049521948df5…
https://git.kernel.org/stable/c/0de9f31d447ae71ab…
https://git.kernel.org/stable/c/2acb9f3d1cc8f65dc…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 3f93aef535c8ea03e40cd8acf0753b3e6ed33e96 , < d8f57049521948df5f50797141472fbbed3b0723 (git) Affected: 3f93aef535c8ea03e40cd8acf0753b3e6ed33e96 , < 0de9f31d447ae71ab08c7850a321682f8d2907c3 (git) Affected: 3f93aef535c8ea03e40cd8acf0753b3e6ed33e96 , < 2acb9f3d1cc8f65dc81ed55e238cbf8e5b60bff7 (git)
Linux	Linux	Affected: 5.1 Unaffected: 0 , < 5.1 (semver) Unaffected: 6.18.53 , ≤ 6.18.* (semver) Unaffected: 7.2.7 , ≤ 7.2.* (semver) Unaffected: 7.3-rc2 , ≤ * (original_commit_for_fix)

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        {
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          "programFiles": [
            "fs/btrfs/zstd.c"
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    "dateReserved": "2026-09-25T10:19:56.074Z",
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}

Sightings

Author	Source	Type	Date	Other

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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 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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GHSA-4XRV-JF38-655F

CVE-2026-98079 (GCVE-0-2026-98079)

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