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CVE Record

CVE-2021-46970: bus: mhi: pci_generic: Remove WQ_MEM_RECLAIM flag from state workqueue

In the Linux kernel, the following vulnerability has been resolved: bus: mhi: pci_generic: Remove WQ_MEM_RECLAIM flag from state workqueue A recent change created a dedicated workqueue for the state-change work with WQ_HIGHPRI (no strong reason for that) and WQ_MEM_RECLAIM flags, but the state-change work (mhi_pm_st_worker) does not guarantee forward progress under memory pressure, and will even wait on various memory allocations when e.g. creating devices, loading firmware, etc... The work is then not part of a memory reclaim path... Moreover, this causes a warning in check_flush_dependency() since we end up in code that flushes a non-reclaim workqueue: [ 40.969601] workqueue: WQ_MEM_RECLAIM mhi_hiprio_wq:mhi_pm_st_worker [mhi] is flushing !WQ_MEM_RECLAIM events_highpri:flush_backlog [ 40.969612] WARNING: CPU: 4 PID: 158 at kernel/workqueue.c:2607 check_flush_dependency+0x11c/0x140 [ 40.969733] Call Trace: [ 40.969740] __flush_work+0x97/0x1d0 [ 40.969745] ? wake_up_process+0x15/0x20 [ 40.969749] ? insert_work+0x70/0x80 [ 40.969750] ? __queue_work+0x14a/0x3e0 [ 40.969753] flush_work+0x10/0x20 [ 40.969756] rollback_registered_many+0x1c9/0x510 [ 40.969759] unregister_netdevice_queue+0x94/0x120 [ 40.969761] unregister_netdev+0x1d/0x30 [ 40.969765] mhi_net_remove+0x1a/0x40 [mhi_net] [ 40.969770] mhi_driver_remove+0x124/0x250 [mhi] [ 40.969776] device_release_driver_internal+0xf0/0x1d0 [ 40.969778] device_release_driver+0x12/0x20 [ 40.969782] bus_remove_device+0xe1/0x150 [ 40.969786] device_del+0x17b/0x3e0 [ 40.969791] mhi_destroy_device+0x9a/0x100 [mhi] [ 40.969796] ? mhi_unmap_single_use_bb+0x50/0x50 [mhi] [ 40.969799] device_for_each_child+0x5e/0xa0 [ 40.969804] mhi_pm_st_worker+0x921/0xf50 [mhi]

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This CVE covers a Linux kernel MHI bus bug where a high-priority state workqueue was marked for memory reclaim even though its work can block on allocations. The source describes kernel warnings and unsafe reclaim assumptions, not a confirmed remote attack path.

Executive priority

Treat as a kernel maintenance item unless your fleet depends on MHI hardware paths. There is no source-backed active exploitation signal, but affected kernels should be updated through normal security patch channels.

Technical view

In bus/mhi/pci_generic, mhi_pm_st_worker used a WQ_MEM_RECLAIM workqueue without guaranteeing forward progress under memory pressure. It may create devices, load firmware, or flush non-reclaim workqueues, triggering check_flush_dependency warnings. Stable kernel commits remove the inappropriate flag.

Likely exposure

Exposure appears limited to Linux systems running affected kernel versions or commits containing the MHI PCI generic workqueue change, especially where the MHI subsystem is used. The bundle lists Linux 5.11, 5.11.20, 5.12.3, and 5.13 as affected, but product-level scope is incomplete.

Exploitation context

The provided sources do not show CISA KEV listing, active exploitation, exploit availability, or attacker prerequisites. Evidence is a kernel correctness and reliability issue around workqueue reclaim behavior, with warnings shown during MHI device teardown paths.

Researcher notes

The CVE text identifies a WQ_MEM_RECLAIM misuse, not a complete exploit chain. The impact is not quantified with CVSS or CWE data in the bundle. Analysis should focus on affected kernel lineage, MHI driver presence, and whether distro kernels backported the stable commits.

Mitigation direction

  • Upgrade to a supported kernel containing the referenced stable fixes.
  • Check Linux distribution advisories for backported fixes to your kernel package.
  • Prioritize systems using the MHI PCI generic driver or related hardware paths.
  • Avoid direct wrangler or deployment assumptions; follow vendor kernel maintenance guidance.

Validation and detection

  • Inventory kernel versions against the affected versions in the CVE bundle.
  • Confirm whether the MHI subsystem or pci_generic driver is built or loaded.
  • Check kernel package changelogs for commits abd1510c, ed541cff, or 0fccbf0a.
  • Review dmesg or logs for the cited workqueue reclaim warning.
  • Regression-test MHI-connected devices after kernel updates.
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

Conservative CVE-to-ATT&CK context

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CVE-2021-46970 mapping review

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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
2ADP providers
4Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

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

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux8f70397876872789b2a5deba804eb6216fb5deb7, 8f70397876872789b2a5deba804eb6216fb5deb7, 8f70397876872789b2a5deba804eb6216fb5deb7unaffected
LinuxLinux5.11, 0, 5.11.20, 5.12.3, 5.13affected
Weakness

CWE details

No CWE listed

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