Vulnerability-Lookup

GHSA-JFR9-726H-GV8R

Vulnerability from github – Published: 2025-02-27 03:34 – Updated: 2025-02-27 21:32

Details

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

workqueue: Put the pwq after detaching the rescuer from the pool

The commit 68f83057b913("workqueue: Reap workers via kthread_stop() and remove detach_completion") adds code to reap the normal workers but mistakenly does not handle the rescuer and also removes the code waiting for the rescuer in put_unbound_pool(), which caused a use-after-free bug reported by Cheung Wall.

To avoid the use-after-free bug, the pool’s reference must be held until the detachment is complete. Therefore, move the code that puts the pwq after detaching the rescuer from the pool.

Severity

7.8 (High)


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

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{
  "affected": [],
  "aliases": [
    "CVE-2025-21786"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-416"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-02-27T03:15:19Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nworkqueue: Put the pwq after detaching the rescuer from the pool\n\nThe commit 68f83057b913(\"workqueue: Reap workers via kthread_stop() and\nremove detach_completion\") adds code to reap the normal workers but\nmistakenly does not handle the rescuer and also removes the code waiting\nfor the rescuer in put_unbound_pool(), which caused a use-after-free bug\nreported by Cheung Wall.\n\nTo avoid the use-after-free bug, the pool\u2019s reference must be held until\nthe detachment is complete. Therefore, move the code that puts the pwq\nafter detaching the rescuer from the pool.",
  "id": "GHSA-jfr9-726h-gv8r",
  "modified": "2025-02-27T21:32:15Z",
  "published": "2025-02-27T03:34:06Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-21786"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/835b69c868f53f959d4986bbecd561ba6f38e492"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e76946110137703c16423baf6ee177b751a34b7e"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e7c16028a424dd35be1064a68fa318be4359310f"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2025-21786 (GCVE-0-2025-21786)

Vulnerability from cvelistv5 – Published: 2025-02-27 02:18 – Updated: 2026-08-05 11:54

Title

workqueue: Put the pwq after detaching the rescuer from the pool

Summary

In the Linux kernel, the following vulnerability has been resolved: workqueue: Put the pwq after detaching the rescuer from the pool The commit 68f83057b913("workqueue: Reap workers via kthread_stop() and remove detach_completion") adds code to reap the normal workers but mistakenly does not handle the rescuer and also removes the code waiting for the rescuer in put_unbound_pool(), which caused a use-after-free bug reported by Cheung Wall. To avoid the use-after-free bug, the pool’s reference must be held until the detachment is complete. Therefore, move the code that puts the pwq after detaching the rescuer from the pool.

Severity

7.8 (High)


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

SSVC

Exploitation: none Automatable: no Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2025-02-27 18:14 UTC

CWE

CWE-416 - Use After Free

Assigner

Linux mitre root

References

3 references

URL	Tags
https://git.kernel.org/stable/c/e7c16028a424dd35b…
https://git.kernel.org/stable/c/835b69c868f53f959…
https://git.kernel.org/stable/c/e76946110137703c1…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 68f83057b913467a999e1bf9e0da6a119668f769 , < e7c16028a424dd35be1064a68fa318be4359310f (git) Affected: 68f83057b913467a999e1bf9e0da6a119668f769 , < 835b69c868f53f959d4986bbecd561ba6f38e492 (git) Affected: 68f83057b913467a999e1bf9e0da6a119668f769 , < e76946110137703c16423baf6ee177b751a34b7e (git)
Linux	Linux	Affected: 6.11 Unaffected: 0 , < 6.11 (semver) Unaffected: 6.12.16 , ≤ 6.12.* (semver) Unaffected: 6.13.4 , ≤ 6.13.* (semver) Unaffected: 6.14 , ≤ * (original_commit_for_fix)

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              "attackComplexity": "LOW",
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              "confidentialityImpact": "HIGH",
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              "scope": "UNCHANGED",
              "userInteraction": "NONE",
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        }
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              "value": "AV:L - The vulnerability is in the core workqueue rescuer path and is reached by generating local workqueue load and memory pressure; there is no remote input path into `rescuer_thread()`. Exploitation requires the attacker to be executing code on the system.\nAC:L - The attacker fully controls the side of the race that matters \u2014 sustained memory pressure plus queued work on an unbound `WQ_MEM_RECLAIM` workqueue drives `pool_mayday_timeout()`/`send_mayday()` at will and can be looped indefinitely, so the narrow window between `put_pwq()` and `worker_detach_from_pool()` can be retried unboundedly until the RCU free lands first.\nPR:L - Any unprivileged local user can create the required conditions \u2014 allocating memory to stall `create_worker()` and issuing filesystem/block/network I/O that queues work on unbound `WQ_MEM_RECLAIM` workqueues (ext4-rsv-conversion, xfs, nfsiod, rpciod, scsi hosts). No capability check guards the rescuer path.\nUI:N - The rescuer is summoned automatically by the workqueue watchdog timer under memory pressure; no action by any other user or administrator-victim is needed to complete the attack.\nS:U - The freed object and the corruption both live in kernel heap memory within the same security authority; there is no VM, IOMMU, or sandbox boundary crossed.\nC:H - The freed `struct worker_pool` is read after free (`pool-\u003eflags`, `worker-\u003enode` list pointers) and comes from a generic kmalloc cache, so a reallocated victim object leaks its contents through the rescuer\u0027s list manipulation, giving a path to arbitrary kernel memory disclosure.\nI:H - `detach_worker()`\u0027s `list_del(\u0026worker-\u003enode)` performs a write-after-free of kernel pointers at the fixed offset of `pool-\u003eworkers` into the freed slab object, which after heap spraying yields a controlled-offset write primitive usable for control-flow hijack and privilege escalation.\nA:H - Use-after-free on the worker pool corrupts the attached-workers list and typically produces an immediate oops/panic (KASAN reported it as a UAF), permanently wedging or crashing the kernel."
            }
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Sightings

Author	Source	Type	Date	Other

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.

Detection rules are retrieved from Rulezet.

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 model, served locally by ML-Gateway. 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.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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