[CVE-2026-90385][LOW] md/raid1: create serial pool adding rdev to array with serialize_policy=1 [ Upstream

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

CVE: CVE-2026-90385
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: md/raid1: create serial pool adding rdev to array with serialize_policy=1 [ Upstream
Commit: f9e4364449f7ca6917f3599eb32064dba5b7b147
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f9e4364449f7ca6917f3599eb32064dba5b7b147
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90385
Analysis date: Thu, 17 Sep 2026 20:00:15 -0400
ActionableScore: 0
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-2026-90385 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90385

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-2026-90385	LOW	https://www.kernelcve.org/list/?q=CVE-2026-90385 CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';**CWE-476;CWE-665;CWE-754;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'Adding a new rdev to an existing RAID1 array with serialize_policy enabled can leave rdev serial uninitialized. Later raid1 I/O can enter wait_for_serialization, assume the serial object exists, and dereference it in the locking path, causing a NULL pointer dereference and kernel crash. For the CVSS the PR:L is used in the paranoid score only for environments where a less privileged local service or delegated admin context can add rdevs or trigger md reconfiguration. In typical deployments this operation requires full local administrator privileges, so the base score uses PR:H. The issue is not network reachable and requires local storage management access. Impact is denial of service only via kernel crash, with no evidence of information disclosure or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0)	YES	DISK HARDWARE LINUS  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	NO	NO	checked

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

ActionableScore=0
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=YES
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: -1
* Conservative score: 0. Applied lower bound clamp: -1 -> 0.
* Raw paranoid score: -1
* Paranoid score: 0. Applied lower bound clamp: -1 -> 0.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

Positive signals:

* +1 Reliable kernel crash / strong DoS: the supplied trace shows an Oops in `_raw_spin_lock_irqsave()` through `wait_for_serialization()` after RAID1 I/O reaches an uninitialized `rdev->serial`.
* +0 Storage path importance: this is in md/raid1 I/O handling, but no storage metadata corruption, ownership violation, data corruption, or persistent filesystem damage is established.

Negative signals:

* -2 Host-admin-equivalent privilege required: adding a new `rdev` to an existing md RAID array and configuring `serialize_policy` are host storage administration operations.

Material non-awarded signals:

* RealUAF not awarded: the bug is an uninitialized or missing `rdev->serial` allocation, not post-free object use.
* Concrete repeated release/refcount not awarded: no first release, surviving dangling reference, or second lifetime-mutating operation is shown.
* Controlled reclaim not demonstrated.
* Arbitrary or directed kernel write not demonstrated.
* Confidentiality and integrity impact not awarded.
* Remote reachability not established.
* Extra Availability not awarded because the Oops/kernel crash is already counted once.
* Weak LPE and strong exploitation leverage not awarded because the established primitive is a NULL pointer dereference only.

Repeated release/refcount checklist:

* First release can end lifetime: no.
* Exact same reference survives after release: no.
* Second operation mutates lifetime/refcount: no.
* Concrete repeated release/refcount +1 awarded: no.
* Paranoid repeated-refcount leverage +1 awarded: no.
* FLOOR 5 applied: no.

3. Reachability analysis

The complete trigger requires md RAID management: an existing RAID1 array with `serialize_policy=1`, adding a new `rdev`, and then causing RAID1 I/O that enters `wait_for_serialization()`. These operations are normally controlled by host storage administrators through md/sysfs or equivalent tooling. The supplied trace also shows UID 0 context.

No namespace-scoped complete trigger is established. There is no evidence that an ordinary unprivileged user can create or reconfigure the relevant md array, add an `rdev`, or set `serialize_policy` in an attacker-created namespace. No network trigger is present. No special rare hardware is required beyond md RAID usage, but that does not increase the score because the reachable operation is host-admin storage management. This is not a race. It is an ordered configuration/state bug.

4. Primitive and severity interpretation

The exact primitive is a NULL pointer dereference caused by skipping creation of `rdev->serial` when adding a new RAID1 member to an array with `MD_SERIALIZE_POLICY` already enabled. Later RAID1 I/O assumes `rdev->serial` exists and passes into the serialization lock path, causing a kernel Oops.

This is not an active structured UAF and not fixed stale storage after free. It is missing initialization of required per-rdev state. There is no concrete repeated release/refcount mutation. There is no evidence of controlled memory corruption, object replacement, page ownership corruption, arbitrary write, information disclosure, or privilege escalation.

PrimitiveClass is CLASS_C because the demonstrated behavior is crash/DoS from invalid state and NULL dereference. ImportantCandidate is NO because no Important-grade exploitation leverage is established. AutoDowngradeAllowed is YES because the issue is host-admin-triggered, crash-only, and lacks unresolved memory corruption or security-boundary bypass.

Likely operational severity: low actionable priority / ordinary Moderate. It should be fixed through normal kernel update flow, but it does not require urgent manual exploitation review from the supplied evidence.

5. One-sentence report phrase

Adding a new rdev to a RAID1 array with serialize_policy enabled can leave rdev serial uninitialized, causing a NULL pointer dereference and kernel crash during later RAID1 I/O, but exploitation requires local host storage administration privileges and has DoS impact only.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: this is a host-admin-gated NULL pointer dereference with demonstrated DoS only and no UAF, repeated lifetime mutation, controlled corruption, information disclosure, privilege escalation, or network reachability.

7. Call-site confidence

Call-site confidence: high

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

Patch: md/raid1: create serial pool adding rdev to array with serialize_policy=1 [ Upstream
Commit: f9e4364449f7ca6917f3599eb32064dba5b7b147
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f9e4364449f7ca6917f3599eb32064dba5b7b147

Changed files:
  drivers/md/md.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=f9e4364449f7ca6917f3599eb32064dba5b7b147

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

The original Linux kernel CVE announcement for CVE-2026-90385 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90385

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:L/PR:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.5

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: 0

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).