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CVE Record

CVE-2025-21983: mm/slab/kvfree_rcu: Switch to WQ_MEM_RECLAIM wq

In the Linux kernel, the following vulnerability has been resolved: mm/slab/kvfree_rcu: Switch to WQ_MEM_RECLAIM wq Currently kvfree_rcu() APIs use a system workqueue which is "system_unbound_wq" to driver RCU machinery to reclaim a memory. Recently, it has been noted that the following kernel warning can be observed: <snip> workqueue: WQ_MEM_RECLAIM nvme-wq:nvme_scan_work is flushing !WQ_MEM_RECLAIM events_unbound:kfree_rcu_work WARNING: CPU: 21 PID: 330 at kernel/workqueue.c:3719 check_flush_dependency+0x112/0x120 Modules linked in: intel_uncore_frequency(E) intel_uncore_frequency_common(E) skx_edac(E) ... CPU: 21 UID: 0 PID: 330 Comm: kworker/u144:6 Tainted: G E 6.13.2-0_g925d379822da #1 Hardware name: Wiwynn Twin Lakes MP/Twin Lakes Passive MP, BIOS YMM20 02/01/2023 Workqueue: nvme-wq nvme_scan_work RIP: 0010:check_flush_dependency+0x112/0x120 Code: 05 9a 40 14 02 01 48 81 c6 c0 00 00 00 48 8b 50 18 48 81 c7 c0 00 00 00 48 89 f9 48 ... RSP: 0018:ffffc90000df7bd8 EFLAGS: 00010082 RAX: 000000000000006a RBX: ffffffff81622390 RCX: 0000000000000027 RDX: 00000000fffeffff RSI: 000000000057ffa8 RDI: ffff88907f960c88 RBP: 0000000000000000 R08: ffffffff83068e50 R09: 000000000002fffd R10: 0000000000000004 R11: 0000000000000000 R12: ffff8881001a4400 R13: 0000000000000000 R14: ffff88907f420fb8 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff88907f940000(0000) knlGS:0000000000000000 CR2: 00007f60c3001000 CR3: 000000107d010005 CR4: 00000000007726f0 PKRU: 55555554 Call Trace: <TASK> ? __warn+0xa4/0x140 ? check_flush_dependency+0x112/0x120 ? report_bug+0xe1/0x140 ? check_flush_dependency+0x112/0x120 ? handle_bug+0x5e/0x90 ? exc_invalid_op+0x16/0x40 ? asm_exc_invalid_op+0x16/0x20 ? timer_recalc_next_expiry+0x190/0x190 ? check_flush_dependency+0x112/0x120 ? check_flush_dependency+0x112/0x120 __flush_work.llvm.1643880146586177030+0x174/0x2c0 flush_rcu_work+0x28/0x30 kvfree_rcu_barrier+0x12f/0x160 kmem_cache_destroy+0x18/0x120 bioset_exit+0x10c/0x150 disk_release.llvm.6740012984264378178+0x61/0xd0 device_release+0x4f/0x90 kobject_put+0x95/0x180 nvme_put_ns+0x23/0xc0 nvme_remove_invalid_namespaces+0xb3/0xd0 nvme_scan_work+0x342/0x490 process_scheduled_works+0x1a2/0x370 worker_thread+0x2ff/0x390 ? pwq_release_workfn+0x1e0/0x1e0 kthread+0xb1/0xe0 ? __kthread_parkme+0x70/0x70 ret_from_fork+0x30/0x40 ? __kthread_parkme+0x70/0x70 ret_from_fork_asm+0x11/0x20 </TASK> ---[ end trace 0000000000000000 ]--- <snip> To address this switch to use of independent WQ_MEM_RECLAIM workqueue, so the rules are not violated from workqueue framework point of view. Apart of that, since kvfree_rcu() does reclaim memory it is worth to go with WQ_MEM_RECLAIM type of wq because it is designed for this purpose.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This Linux kernel issue is about memory-reclaim work being queued on the wrong type of workqueue. The cited failure is a kernel warning during NVMe namespace scanning, not a demonstrated compromise. Business urgency depends on whether your fleet runs the affected Linux kernel versions and whether stability of storage-heavy systems is critical.

Executive priority

Treat as a stability and maintenance item unless your vendor rates it higher. It does not currently justify emergency response based on the supplied evidence, but kernel patch planning should include it for affected systems.

Technical view

kvfree_rcu() used system_unbound_wq for RCU memory reclamation. The kernel workqueue framework warned when WQ_MEM_RECLAIM work flushed non-WQ_MEM_RECLAIM kfree_rcu_work. The fix switches kvfree_rcu reclaim work to an independent WQ_MEM_RECLAIM workqueue, aligning reclaim behavior with workqueue rules.

Likely exposure

Exposure is limited to systems running affected Linux kernel versions listed in the source bundle. The source indicates Linux kernels including 6.12, 6.12.20, 6.13.8, and 6.14 entries, but version range normalization is incomplete in the bundle.

Exploitation context

No active exploitation is supported by the provided sources. The CVE is not marked KEV, has no CVSS or CWE in the bundle, and the public description centers on a kernel warning and memory-reclaim correctness issue.

Researcher notes

The observable symptom is a workqueue dependency warning involving kvfree_rcu_barrier(), kmem_cache_destroy(), bioset_exit(), and nvme_scan_work. The fix changes workqueue attributes, not an exposed API. Impact beyond warning or reclaim behavior is not established in the supplied sources.

Mitigation direction

  • Check your distribution kernel advisory for CVE-2025-21983.
  • Update to a kernel containing one of the referenced stable commits.
  • Prioritize storage-heavy systems if kernel warnings affect availability.
  • Avoid inventing local workarounds without vendor guidance.

Validation and detection

  • Inventory Linux kernel versions across servers and appliances.
  • Compare deployed kernels with vendor advisories for CVE-2025-21983.
  • Check kernel logs for the cited workqueue warning pattern.
  • Confirm patched builds include the referenced stable kernel commits.
Prepared
Confidence
medium
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
0ADP providers
4Source links

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

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Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux6c6c47b063b593785202be158e61fe5c827d6677, 6c6c47b063b593785202be158e61fe5c827d6677, 6c6c47b063b593785202be158e61fe5c827d6677unaffected
LinuxLinux6.12, 0, 6.12.20, 6.13.8, 6.14affected
Weakness

CWE details

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