[CVE-2026-90283][LOW] hugetlbfs: release subpool on fill_super failure [ Upstream

[CVE-2026-90283][LOW] hugetlbfs: release subpool on fill_super failure [ Upstream

[AL-KERNEL]

CVE: CVE-2026-90283
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: hugetlbfs: release subpool on fill_super failure [ Upstream
Commit: f2d6cea221d777fab3ba18f805ba4c17c90e0b8b
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f2d6cea221d777fab3ba18f805ba4c17c90e0b8b
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90283
Analysis date: Thu, 17 Sep 2026 17:13:39 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
hugetlbfs may leave hugepage min_size reservations charged when `hugetlbfs_fill_super()` fails after subpool creation, causing a local resource leak that can potentially lead to denial of service through repeated failed mounts.

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

The original Linux kernel CVE announcement for CVE-2026-90283 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90283

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-2026-90283	LOW	https://www.kernelcve.org/list/?q=CVE-2026-90283 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-772;*CWE-401;**CWE-400;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'hugetlbfs can leave huge page min_size reservations charged when hugetlbfs_fill_super fails after creating a subpool because the failure path used direct kfree instead of the normal subpool release path. This is a resource leak rather than a memory corruption primitive and the practical impact is local denial of service through gradual exhaustion of reserved huge pages. For the CVSS the PR:L is used for the paranoid interpretation because some container or delegated environments may expose mount capability to less trusted local users, while the normal host scenario is administrative mount control. The issue is not network reachable and is triggered through local hugetlbfs mount failure handling rather than external traffic. Reliable triggering also depends on hitting the allocation failure path after subpool creation, so the attack complexity is high.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)	YES	DISK SIMPLEFIX LINUS MEMORY  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=2
ActionableScoreLower=1
PrimitiveClass=NONE
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
* Applied conservative floor/cap: none
* Applied paranoid floor/cap: none
* Final recommended bucket: **Ordinary Moderate**::

## 2. Signal breakdown

Conservative signals:

* +1 Concrete persistent kernel resource/reference leak. `hugetlbfs_fill_super()` creates a hugepage subpool and the failure path used `kfree()` instead of `hugepage_put_subpool()`, leaving `min_size` hugepage reservations charged.
* +0 Reliable kernel crash / strong DoS not awarded. The patch supports a resource reservation leak, not an immediate panic or fatal fault.
* +0 Local unprivileged trigger not awarded. Mount reachability below host admin is not fully established by the supplied evidence.
* +0 C/I impact not awarded. No information disclosure, unauthorized data modification, memory corruption, UAF, OOB access, or authorization bypass is established.
* +0 Remote reachability not awarded. The trigger is local hugetlbfs mount failure handling, not packet or network input.

Paranoid additional signal:

* +1 Sustained resource exhaustion concern. Repeated failed hugetlbfs mounts after subpool creation could plausibly accumulate charged hugepage reservations and degrade availability.

Important non-awarded signals:

* Real UAF not awarded. The issue is a missing semantic release path for reservations, not demonstrated post-free object use.
* Concrete repeated release/refcount not awarded. There is no first release followed by a second lifetime mutation on the exact same dangling reference.
* Strong exploitation leverage not awarded. No controlled reclaim, arbitrary write, callback control, refcount takeover, or LPE path is supported.
* Race/timing penalty not applied. This is an error-path sequence, not a demonstrated hard race.
* Host-admin penalty not applied. Host-admin-equivalent privilege is plausible for mounting, but the prompt requires positive proof for that penalty.

## 3. Reachability analysis

The trigger requires creating a hugetlbfs mount with `size` or `min_size` so that `hugepage_new_subpool()` creates a subpool and may reserve huge pages. The vulnerable path is reached only if a later allocation step, specifically root dentry creation, fails after the subpool exists.

The complete privilege boundary is unresolved from the supplied patch alone. Mount operations are commonly privileged, but hugetlbfs and namespace behavior can be configuration dependent, so `HostAdminRequired=UNKNOWN` and `NamespaceScopedPrivilege=UNKNOWN` are safer than assuming either host root or ordinary user reachability. Prior hugepage availability and relevant mount capability are prerequisites. No network trigger, special hardware, firmware path, or race is involved.

## 4. Primitive and severity interpretation

The exact primitive is a persistent hugepage reservation/resource leak caused by using `kfree()` instead of the subpool release helper. This bypasses the normal release logic that drops subpool accounting and reservations.

This is not active structured stale-object use and not fixed stale storage UAF. No concrete repeated release/refcount operation exists. The demonstrated consequence is local resource leakage. The plausible worst case is local DoS through accumulated hugepage reservation exhaustion. There is no patch-supported confidentiality impact, integrity impact, privilege escalation, authorization bypass, or memory corruption primitive.

`PrimitiveClass=NONE` because the issue is resource accounting/lifetime cleanup failure without a meaningful corruption or security-boundary primitive. `ImportantCandidate=NO` because the evidence does not create Important-vs-Moderate ambiguity. `AutoDowngradeAllowed=YES` because this is a constrained resource leak with no unresolved memory-corruption or boundary-bypass leverage.

## 5. One-sentence report phrase

hugetlbfs may leave hugepage min_size reservations charged when `hugetlbfs_fill_super()` fails after subpool creation, causing a local resource leak that can potentially lead to denial of service through repeated failed mounts.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: this is a resource leak without UAF, memory corruption, authorization bypass, remote reachability, or plausible privilege escalation, and the paranoid score remains low.

## 7. Call-site confidence

Call-site confidence: high

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

Patch: hugetlbfs: release subpool on fill_super failure [ Upstream
Commit: f2d6cea221d777fab3ba18f805ba4c17c90e0b8b
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f2d6cea221d777fab3ba18f805ba4c17c90e0b8b

Changed files:
  fs/hugetlbfs/inode.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=f2d6cea221d777fab3ba18f805ba4c17c90e0b8b

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

The original Linux kernel CVE announcement for CVE-2026-90283 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90283

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:L
  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).