[CVE-2026-90184][LOW] null_blk: serialize configfs attribute updates with device setup [ Upstream

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-90184
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: null_blk: serialize configfs attribute updates with device setup [ Upstream
Commit: 6352e7ead2d8111802a554eeb94886f5a9894bb9
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6352e7ead2d8111802a554eeb94886f5a9894bb9
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90184
Analysis date: Fri, 18 Sep 2026 00:02:39 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
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-2026-90184 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90184

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-2026-90184	LOW	https://www.kernelcve.org/list/?q=CVE-2026-90184 CHECK WITH IMPACT FROM ORIG NN 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-362;CWE-667;**CWE-476;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 race in null_blk configfs handling can allow device attributes to change while null_add_dev is still building the device. This can make different parts of setup observe inconsistent values such as dev zoned changing between queue limit setup and zone resource initialization. In the worst described case a zoned disk can be added without initialized zone resources, and the first write path can dereference a NULL zones pointer and crash the kernel. For the CVSS the PR:L is used in the paranoid score because some environments may delegate null_blk or configfs control to a reduced capability admin or test service account. The issue is not network reachable and requires local control of null_blk configfs attributes. Impact is denial of service via kernel crash, with no concrete evidence of information disclosure or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)	YES	LOCK INIT WARNONLY HARDWARE TEST SYZBOT 	NO	NO	checked

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

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

1. ActionableScore

* Raw conservative score: 2
* Conservative score: 2. No floor or cap applied.
* Raw paranoid score: 2
* Paranoid score: 2. No floor or cap applied.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

Positive signals:

* +1 Weak invalid-state primitive. Unsynchronized configfs attribute updates can make `null_add_dev()` observe inconsistent `dev->zoned` state during device setup.
* +1 Reliable kernel crash / strong DoS. The commit states that a zoned disk can be added without initialized zone resources, and `null_process_zoned_cmd()` can later dereference `dev->zones == NULL` on the first write.

Negative signals:

* 0 No host-admin penalty applied. `null_blk` configfs control is normally administrative, but the supplied evidence does not fully prove the complete privilege boundary for every evaluated deployment.
* 0 No race penalty applied. The bug is a race, but the concurrent operations are ordinary configfs writes that can be repeated by whoever can control the device attributes.

Important non-awarded signals:

* No UAF or stale post-lifetime object use is established.
* No concrete repeated release/refcount mutation exists.
* Controlled reclaim is not demonstrated.
* Arbitrary or directed kernel write is not demonstrated.
* Confidentiality and integrity impact are not awarded.
* Remote reachability is not established.
* Extra availability is not awarded because the NULL dereference crash is already counted once.
* Strong LPE, weak LPE, and structured stale-object leverage are not awarded because the patch supports invalid state plus NULL dereference DoS, not a reusable corruption primitive.

3. Reachability analysis

The trigger requires local ability to modify `null_blk` configfs attributes such as `power` and `zoned` concurrently. In normal deployments this is expected to be restricted to host administrator or trusted test infrastructure, because `null_blk` configfs device management is not an ordinary unprivileged user API.

Host-admin-equivalent privilege is not marked as positively established because the supplied snippet does not include file permissions, mount policy, or product-specific delegation. Namespace-scoped privilege is not established. This is not a network-triggered issue and no packet path is involved.

No special physical hardware is required because `null_blk` is a synthetic block driver. A prior kernel configuration or module availability is needed, but the scoring does not apply a rare-subsystem penalty merely because the driver is optional. The race appears repeatable by a user who can perform the relevant configfs writes.

4. Primitive and severity interpretation

The exact primitive is an inconsistent live configuration state during `null_add_dev()`. Different setup stages can observe different values of `dev->zoned`, which can result in a zoned disk state without initialized zone resources.

This is not an active structured-object UAF and not fixed stale storage. It is best classified as CLASS_C invalid-state / NULL-pointer dereference behavior. The demonstrated consequence is kernel crash / DoS. A stronger consequence such as privilege escalation is speculative and not supported by the patch.

ImportantCandidate=NO because there is no concrete memory corruption primitive beyond NULL dereference, no UAF, no repeated lifetime mutation, no controlled overwrite, and no authorization bypass. AutoDowngradeAllowed=YES because the issue is a local control-plane DoS with no unresolved Important-grade primitive.

5. One-sentence report phrase

A race in null_blk configfs attribute handling can let device configuration change during setup, causing inconsistent zoned-device state and a later NULL-pointer dereference that results in a local kernel crash.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: the evidence supports a local NULL dereference DoS in a configfs-controlled test block driver, without UAF, repeated refcount mutation, controlled corruption, remote reachability, or authorization-boundary impact.

7. Call-site confidence

Call-site confidence: high

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

Patch: null_blk: serialize configfs attribute updates with device setup [ Upstream
Commit: 6352e7ead2d8111802a554eeb94886f5a9894bb9
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6352e7ead2d8111802a554eeb94886f5a9894bb9

Changed files:
  block/blk-zoned.c
  block/6a7d0b3f.ac361c09.22ff0a.004c.GAE
  drivers/block/null_blk/main.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=6352e7ead2d8111802a554eeb94886f5a9894bb9

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

The original Linux kernel CVE announcement for CVE-2026-90184 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90184

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: unknown
  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).