[CVE-2026-90144][LOW] dpll: fix NULL deref in dpll_device_ops() during teardown race [ Upstream

[CVE-2026-90144][LOW] dpll: fix NULL deref in dpll_device_ops() during teardown race [ Upstream

[AL-KERNEL]

CVE: CVE-2026-90144
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: dpll: fix NULL deref in dpll_device_ops() during teardown race [ Upstream
Commit: fdbf04e3e01a872d0ef2149f846f1a3e3cb54f5b
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fdbf04e3e01a872d0ef2149f846f1a3e3cb54f5b
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90144
Analysis date: Thu, 17 Sep 2026 23:44:35 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-90144 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90144

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-2026-90144	LOW	https://www.kernelcve.org/list/?q=CVE-2026-90144 CHECK WITH IMPACT FROM ORIG NN MODERATE	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-362;**CWE-476;*CWE-664;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'A teardown race in the dpll core can leave a live dpll object with an empty registration list while a queued pin notification still walks pin dpll_refs and resolves device operations through dpll_device_ops(). This can trigger a WARN and then a NULL pointer dereference when the missing registration is dereferenced, causing a kernel crash or workqueue failure. For the CVSS the PR:L is used in the paranoid score because some deployments may delegate network device or dpll management to a service account, container root, or a user with limited capabilities rather than full host root. The issue is not directly network reachable and normally requires local control over driver teardown, device unregister, or related dpll control plane operations. Impact is denial of service only. The patch context supports a NULL dereference in a teardown race, not a proven UAF, information leak, arbitrary write, or privilege escalation primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)	YES	DANGER NULLPTR INIT RACE HARDWARE LINUS  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	YES	NO	checked

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

ActionableScore=2
ActionableScoreLower=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 2
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate**::

No floor or cap was applied. The paranoid score is emitted as ActionableScore because it is higher than the conservative score.

2. Signal breakdown

Conservative signals:

* +1 Reliable kernel crash / strong DoS: the trace shows WARN followed by NULL pointer dereference in dpll_device_ops() from queued pin notification work.
* +1 Weak / indirect corruption candidate: the bug is an invalid object state where a live dpll object has an empty registration list and callers dereference missing registration-derived ops.
* -1 Hard or unreliable race / special timing: the demonstrated trigger depends on teardown ordering where notification work was queued before unregister acquired dpll_lock, a narrow asynchronous teardown race.

Conservative total: 1.

Paranoid signals:

* +1 Reliable kernel crash / strong DoS: NULL pointer dereference can crash the kernel or fail the workqueue path.
* +1 Weak / indirect corruption candidate: callers resolve device ops through a registration that may no longer exist.

Paranoid total: 2. The paranoid score withholds the timing penalty but does not add speculative memory-corruption or LPE points.

Non-awarded signals:

* RealUAF not awarded: the commit says the dpll object stays alive, but its registration_list is empty. This is a live object in invalid transient state, not established post-lifetime use of a freed dpll object.
* Concrete repeated release/refcount not awarded: no first release followed by a second lifetime-mutating operation on the exact same dangling reference is shown.
* Structured stale-object leverage not awarded: the stale/invalid use is a missing registration dereference leading to NULL deref, not attacker-controlled reuse or meaningful post-free structured processing.
* Weak LPE and Strong LPE not awarded: no controlled reclaim, arbitrary write, callback hijack, credential impact, refcount takeover, or security-boundary bypass is established.
* Remote reachability not awarded: no packet or remote protocol path reaches the vulnerable teardown race directly.
* C/I not awarded: no information disclosure or unauthorized modification primitive is supported.
* Extra Availability not awarded: the same NULL dereference crash is already counted once.

3. Reachability analysis

The demonstrated path involves dpll device teardown while another driver still holds a pin reference and queued notification work later walks pin->dpll_refs. The trace references ice_dpll_wq and zl3073x_i2c removal, suggesting a local driver/device teardown or removal scenario.

Complete below-host-admin reachability is not established. Driver removal, device unregister, and physical device teardown are commonly host-admin or hardware-management operations, but the supplied evidence does not prove that host-admin-equivalent privilege is always required. Therefore HostAdminRequired is UNKNOWN rather than YES.

NamespaceScopedPrivilege is UNKNOWN. The patch touches dpll netlink paths, but the complete trigger also depends on device registration state and driver teardown. The supplied evidence does not establish that all required stages are reachable inside attacker-created namespaces.

No direct network trigger is established. Prior device and driver setup is required in practice because the bug depends on dpll-capable hardware or drivers such as ice and zl3073x_i2c. This is hardware-specific, but the evidence does not justify a rare-hardware penalty beyond the already low score.

The race is a teardown race with queued work. It appears less repeatable than a normal user-controlled create/destroy loop, which supports the conservative timing penalty.

4. Primitive and severity interpretation

The exact primitive is a NULL pointer dereference caused by treating an empty dpll registration list as impossible. A live dpll object remains referenced through pin->dpll_refs, but its registration list can be empty after unregister. dpll_device_ops() previously assumed a registration existed and dereferenced the missing registration.

This is active kernel object state, but not a demonstrated UAF. The object is not shown to be freed and reused. The patch changes dpll_priv() and dpll_device_ops() to return NULL when no registration exists and updates dpll pin netlink paths to skip such dead references or return -ENODEV.

This is Class C: demonstrated behavior is crash/DoS/invalid-state handling without an independently useful corruption primitive.

Demonstrated consequence: kernel NULL pointer dereference / DoS.

Speculative consequence: stronger exploitation is not supported by the supplied patch. There is no evidence of controlled reclaim, arbitrary kernel read/write, callback control, or privilege escalation.

ImportantCandidate=NO because the primitive is a constrained invalid-state NULL dereference in a teardown race, not an unresolved Class B lifetime corruption primitive.

AutoDowngradeAllowed=YES because no meaningful corruption, repeated refcount mutation, security-boundary bypass, or C/I primitive remains unresolved.

Likely operational severity: ordinary Moderate / low-end DoS, mainly relevant for systems using affected dpll-capable drivers and hitting the teardown race.

5. One-sentence report phrase

A dpll teardown race can leave a live device with no registration while queued pin notification work resolves device operations, causing a NULL pointer dereference and local denial of service.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: the supplied evidence supports a NULL dereference crash in a teardown race, but not UAF, repeated release/refcount corruption, controlled memory corruption, network reachability, or privilege escalation.

7. Call-site confidence

Call-site confidence: high

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

Patch: dpll: fix NULL deref in dpll_device_ops() during teardown race [ Upstream
Commit: fdbf04e3e01a872d0ef2149f846f1a3e3cb54f5b
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fdbf04e3e01a872d0ef2149f846f1a3e3cb54f5b

Changed files:
  drivers/dpll/dpll_core.c
  drivers/dpll/dpll_netlink.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=fdbf04e3e01a872d0ef2149f846f1a3e3cb54f5b

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

The original Linux kernel CVE announcement for CVE-2026-90144 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90144

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: AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H
  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: 1
  Paranoid ActionableScore: 2

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).