[CVE-2026-98537][LOW] workqueue: Fix NULL current_pwq deref in flush dependency check

[CVE-2026-98537][LOW] workqueue: Fix NULL current_pwq deref in flush dependency check

[AL-KERNEL]

CVE: CVE-2026-98537
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: workqueue: Fix NULL current_pwq deref in flush dependency check
Commit: 8ffececcb88262389b4f91fed0fe4884b68204bc
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8ffececcb88262389b4f91fed0fe4884b68204bc
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98537
Analysis date: Sat, 24 Oct 2026 02:54:36 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
A locally induced OOM/workqueue interaction can make a pool-manager kworker dereference a NULL `current_pwq`, causing an Oops or panic without a demonstrated corruption primitive.

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ABOUT THIS REPORT
======================================================================

The original Linux kernel CVE announcement for CVE-2026-98537 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98537

The original announcement does not normally provide a security severity
estimate, CVSS assessment, or enough information to determine whether the
reported kernel bug represents a practically relevant security issue.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin. It combines
an autonomous classifier with LLM-assisted technical analysis and a
separate ActionableScore mechanism.

The purpose of this report is to prioritize Linux kernel CVEs before
manual review, identify cases that require prompt investigation, and
support automatic closure of issues that are unlikely to have meaningful
security impact.

Published priority for this report: LOW
Manual review required: NO

A detailed explanation of the methodology and priority rules is included
at the end of this message.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-98537	LOW	https://www.kernelcve.org/list/?q=CVE-2026-98537 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT LOW AEGIS_AS=1 LEGACY=LOW RESULT=SAME (final reconciliation agrees; DECISION: both LOW)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';**CWE-476;CWE-703;BEST CVSS score: '4.7';DESCR 'check_flush_dependency can dereference a NULL worker current_pwq because current_wq_worker only establishes that the caller has PF_WQ_WORKER set. A kworker acting as a pool manager can enter allocation and OOM notifier processing while it is not executing a work item, leaving current_pwq NULL when the notifier flushes work. The demonstrated primitive is a NULL pointer dereference that can cause a kernel oops or panic. There is no evidence of UAF, OOB access, information disclosure, or a write primitive. For the CVSS the PR:L value reflects that reliable intentional triggering requires a local process able to create memory pressure. AC:H reflects the additional need to reach the pool manager allocation and OOM notifier flush path. Impact is limited to availability. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 4.7 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. No severity changing production threshold or specialist override was recorded. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. The independent weaker Aegis shadow evaluated CVSS 2.7 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was LOW. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)	MAYBE	LOCK WARNONLY LINUS TEST 	-	-	checked

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ACTIONABLESCORE ANALYSIS
======================================================================

ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 1.
* Conservative score: 1; no floor or cap applies.
* Raw paranoid score: 1.
* Paranoid score: 1; no separate corruption or boundary effect supports escalation.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +1 Local unprivileged trigger: a local process can create memory pressure contributing to the allocation/OOM-notifier path; host administration is not required.
* +1 Reliable kernel crash/strong DoS: `worker->current_pwq` is demonstrably NULL outside work-item execution, and dereferencing it can produce an Oops or panic.
* -1 Hard/unreliable trigger: intentional triggering requires the pool-manager worker, failed allocation/OOM processing, notifier-driven work flushing, and the relevant worker state to coincide.
* No extra availability point: it would duplicate the same NULL-dereference crash.
* No UAF, OOB read/write, heap corruption, stale lifetime operation, attacker-controlled write, disclosure, or integrity effect is shown.
* NEW52/B5-R does not apply: there is no retry-accumulated index or heap OOB write, and no corrupted structured state is later consumed.
* No authorization decision changes from DENY to ALLOW; B4-PENDING is inapplicable.

3. Reachability analysis

A local process can induce memory pressure, but it does not directly control `current_pwq` or the exact kworker/OOM-notifier interleaving. The vulnerable execution occurs in a kernel pool-manager kworker during worker allocation. No capability, host UID 0, namespace-scoped privilege, prior privileged setup, special hardware, or unusual configuration is evidenced.

4. Primitive and severity reading

The exact primitive is a NULL pointer dereference in a diagnostic `WARN_ONCE()` condition. It is neither active structured-state corruption nor a lifetime violation. The patch adds a NULL guard before following `current_pwq->wq`; the supported consequence is availability loss only. Accordingly this is CLASS_C, not an Important candidate, and ordinary Moderate handling is safe.

5. One-sentence report phrase

A locally induced OOM/workqueue interaction can make a pool-manager kworker dereference a NULL `current_pwq`, causing an Oops or panic without a demonstrated corruption primitive.

6. Manual review advice

NO MANUAL CHECK NEEDED

The patch and trace establish a constrained NULL-dereference DoS with no unresolved corruption or security-boundary primitive.

7. Call-site confidence

Call-site confidence: high

======================================================================
UPSTREAM PATCH SUMMARY
======================================================================

Patch: workqueue: Fix NULL current_pwq deref in flush dependency check
Commit: 8ffececcb88262389b4f91fed0fe4884b68204bc
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8ffececcb88262389b4f91fed0fe4884b68204bc

Commit description:

check_flush_dependency() uses current_wq_worker() to determine whether
the caller is a workqueue worker and then dereferences worker->current_pwq
to test whether the current workqueue is WQ_MEM_RECLAIM.

current_wq_worker() only means that %current has PF_WQ_WORKER set. A
kworker can reach check_flush_dependency() while it is not executing a
work item. One such path is worker_thread() acting as the pool manager,
where create_worker() does GFP_KERNEL allocation and the allocation path
invokes the OOM notifier. In that state worker->current_pwq is NULL
because current_pwq is set only by process_one_work() and cleared again
after the work function returns.

[  416.760634][  T375] Call trace:
[  416.760638][  T375]  check_flush_dependency+0x80/0x120 (P)
[  416.760648][  T375]  __flush_work+0x98/0x224
[  416.760657][  T375]  flush_work+0x30/0x44
[  416.760665][  T375]  ...
[  416.760710][  T375]  blocking_notifier_call_chain+0x58/0xa0
[  416.760719][  T375]  out_of_memory+0xb4/0x458
[  416.760730][  T375]  __alloc_pages_may_oom+0x11c/0x1a8
[  416.760739][  T375]  __alloc_pages_slowpath+0x314/0x46c
[  416.760746][  T375]  __alloc_frozen_pages_noprof+0x110/0x1a4
[  416.760753][  T375]  new_slab+0x12c/0x484
[  416.760759][  T375]  ___slab_alloc+0x7a8/0xc7c
[  416.760765][  T375]  __slab_alloc+0x74/0xd8
[  416.760772][  T375]  __kmalloc_cache_node_noprof+0x2ac/0x304
[  416.760779][  T375]  alloc_worker+0x28/0x60
[  416.760785][  T375]  create_worker+0x4c/0x20c
[  416.760790][  T375]  worker_thread+0xe8/0x2b8
[  416.760796][  T375]  kthread+0x1a8/0x200
[  416.760805][  T375]  ret_from_fork+0x10/0x20

Guard the WQ_MEM_RECLAIM-worker warning with worker->current_pwq. If the
kworker is not currently executing a work item, there is no current
workqueue to diagnose with that warning. The PF_MEMALLOC warning is left
unchanged so explicit reclaim context flushing a !WQ_MEM_RECLAIM target
is still reported.

Fixes: fca839c ("workqueue: warn if memory reclaim tries to flush !WQ_MEM_RECLAIM workqueue")
Cc: stable@vger.kernel.org
Assisted-by: LLM
Signed-off-by: Pavankumar Kondeti <pavan.kondeti@oss.qualcomm.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  kernel/workqueue.c

Diff excerpt:

Not included in this email. See the upstream URL for the full patch.

Full patch:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8ffececcb88262389b4f91fed0fe4884b68204bc

======================================================================
DETAILED REPORT METHODOLOGY
======================================================================

The original Linux kernel CVE announcement for CVE-2026-98537 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98537

The original CVE announcement normally does not include a security-level
estimate. In particular, it may not contain a CVSS assessment, an impact
level, or enough information to determine whether the reported bug is a
practically relevant security issue. One purpose of this parallel CVE list
is to provide that missing technical and prioritization information.

The original goal of the AL-KERNEL project was to prioritize Linux kernel
CVE analysis automatically before manual review. The system can also help
identify non-security issues that may be suitable for automatic closure.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin.

The first analysis stage combines an autonomous classifier with additional
LLM-based analysis. The autonomous classifier runs locally on a CPU and is
based on a backpropagation neural network. Together, these mechanisms
produce a technical vulnerability description, identify likely weakness
types, estimate CVSS severity, and provide input for ActionableScore.

Two CVSS estimates are retained because incomplete kernel vulnerability
information often permits more than one defensible interpretation:

  Conservative CVSS vector: Not available
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

The conservative vector represents a lower-impact interpretation.
The Best/paranoid vector intentionally represents a plausible upper-bound
interpretation and should not automatically be treated as demonstrated
real-world impact.

CVSS may also need to be adjusted for a particular Linux deployment,
because actual reachability, privileges, enabled kernel configuration,
hardware, namespaces, exposed device nodes, and other environmental
conditions can differ significantly between systems.

A separate ActionableScore mechanism evaluates practical remediation
urgency. Its analysis may include reachability, attack prerequisites,
subsystem exposure, memory-corruption characteristics, denial-of-service
reliability, and possible confidentiality, integrity, or
privilege-escalation impact.

  Conservative ActionableScore: unknown
  Paranoid ActionableScore: 1

The final base severity is taken directly from the second tab-separated
field of the AL-KERNEL classification result. ActionableScore does not
replace or independently override that final AL-KERNEL decision, and
if ActionableScore adjusted impact level of ALKERNEL, then you would see
self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7.

For an AL-KERNEL result of MODERATE, this report uses the following
additional presentation split:

  ActionableScore below 5   -> MODERATE REGULAR
  ActionableScore 5 or more -> MODERATE 7.0

The distinction between MODERATE REGULAR and MODERATE 7.0 makes it
possible to identify Moderate issues that should receive manual analysis
and fixes before lower-priority MODERATE REGULAR issues. In many cases,
MODERATE REGULAR fixes may wait for a later rebase or routine update.

There is one override in which MODERATE REGULAR becomes MODERATE 7.0
even when the ActionableScore is below 5. When the AL-KERNEL result
contains the KPANIC flag, a MODERATE result is always presented as
MODERATE 7.0. The KPANIC flag selected with few regexps without
usage of AI at all, so it helps to detect cases when Kernel Crash happens
and similar (to filter False-Negative results from the LLM usage).

KPANIC indicates that a reliable kernel crash, kernel panic, or similarly
serious kernel availability impact was identified by the classification
workflow.

AL-KERNEL base severity for this report: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

These results are intended to support engineering triage. They are
machine-generated estimates, and cases marked for manual review should
be validated by a human security engineer before final disposition.
For more info read docs linked from here: https://kernelcve.org/
(and you can submit you own patch there to generate such a report
for non-existant CVE-id yet).

Note that in many cases this AI tool selects higher severity, than
real is (means you can expect Importants instead of Moderate 7.0 or
Moderates 7.0 instead of regular Moderates). If you see such cases,
please use reply email interface to add additional manual analyses
info to this particular CVE.
And please, please, let me know when you see Lows instead of Importants
or Important instead of Low (because particular for such cases I
need to tune this AI tool to make it better for this one and next similar).
My contact email for such notifications is alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).