[CVE-2026-72224][LOW] nvdimm/btt: Free arenas on btt_init() error paths

[CVE-2026-72224][LOW] nvdimm/btt: Free arenas on btt_init() error paths

[AL-KERNEL]

CVE: CVE-2026-72224
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: nvdimm/btt: Free arenas on btt_init() error paths
Commit: 9ab5293d9ac3f2c4232220e563d04701f5f44607
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9ab5293d9ac3f2c4232220e563d04701f5f44607
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72224
Analysis date: Sat, 15 Aug 2026 04:17:17 -0400
ActionableScore: 1
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A privileged local BTT initialization failure can leak arena allocations in the NVDIMM driver, and repeated failures may cause limited kernel memory exhaustion without evidence of memory corruption or privilege escalation.

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

The original Linux kernel CVE announcement for CVE-2026-72224 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72224

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-2026-72224	LOW	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:H/UI:N/S:U/C:N/I:N/A:H';*CWE-401;*CWE-772;**CWE-400;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.4';DESCR 'nvdimm/BTT can leak arena allocations when btt_init() fails after discover_arenas() or create_arenas() allocated arena structures. The affected error paths returned NULL without releasing the arenas, so repeated failed BTT initialization attempts can gradually consume kernel memory. For the CVSS the PR:H is used because creating or reconfiguring NVDIMM BTT devices and reaching these initialization error paths normally requires administrative control of the persistent memory device. The issue is not network reachable and has no evidence of memory corruption, information disclosure, or privilege escalation. Impact is denial of service only via resource exhaustion, and practical exploitation depends on repeated local administrative operations or failing device configuration.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)	YES	LEAK ERRORPATH UAF DEBUGFS MEMORY  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	NO	NO	checked

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

ActionableScore=1
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate / Low-like**

## 2. Signal breakdown

Triggered signals:

* Availability impact realistic: +1
  Repeated failed BTT initialization can leak kernel memory and may eventually contribute to resource exhaustion.

Subtracting signals:

* Requires admin/root/CAP_* in typical deployments: -2
  Creating, configuring, or reinitializing NVDIMM/BTT devices normally requires administrative control over persistent memory configuration.

* Rare AND difficult-to-reach subsystem/configuration: -1
  NVDIMM/BTT is not a broadly exposed default subsystem and depends on persistent memory hardware and BTT setup.

Not awarded:

* No remote/network trigger.
* No local unprivileged trigger.
* No UAF, double free, OOB write, refcount corruption, type confusion, or arbitrary write.
* No plausible confidentiality or integrity impact.
* No privilege escalation signal.
* No strong memory corruption primitive.

## 3. Reachability analysis

The bug is reachable through BTT initialization failure paths after arena structures have been allocated by `discover_arenas()` or `create_arenas()`. In normal deployments, reaching these paths requires local administrative control over NVDIMM/BTT configuration or device initialization. Containers and namespaces do not materially lower the privilege requirement unless a privileged management service exposes BTT configuration to less trusted users. The path is not network reachable and is tied to relatively uncommon persistent memory hardware and configuration.

Call-site confidence: high, because the relevant error paths and cleanup target are visible in the provided patch.

## 4. Severity interpretation

This behaves like a privileged local resource leak, not an Important-class vulnerability. The realistic impact is memory leakage across failed initialization attempts, with possible resource exhaustion only if the operation can be repeated. There is no evidence of memory corruption, stale object reuse, unauthorized access, privilege escalation, or sensitive data exposure. Paranoid scoring does not materially increase severity because the bug class remains resource exhaustion only.

## 5. One-sentence report phrase

A privileged local BTT initialization failure can leak arena allocations in the NVDIMM driver, and repeated failures may cause limited kernel memory exhaustion without evidence of memory corruption or privilege escalation.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This can be auto-closed for urgent triage purposes because it is a privileged local memory leak in a rare hardware-dependent subsystem, with no supported memory corruption or security-boundary bypass primitive.

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

Patch: nvdimm/btt: Free arenas on btt_init() error paths
Commit: 9ab5293d9ac3f2c4232220e563d04701f5f44607
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9ab5293d9ac3f2c4232220e563d04701f5f44607

Commit description:

The arenas allocated by discover_arenas() or create_arenas() are not
freed on some error paths in btt_init(). This leaks memory when BTT
initialization fails.

Call free_arenas() from the affected error paths to release the
allocations.

[ as: commit message and log edits ]

Fixes: 5212e11 ("nd_btt: atomic sector updates")
Cc: stable@vger.kernel.org
Signed-off-by: Abdun Nihaal <nihaal@cse.iitm.ac.in>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Link: https://patch.msgid.link/20260519-nvdimmleaks-v1-2-592300fb7a43@cse.iitm.ac.in
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/nvdimm/btt.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=9ab5293d9ac3f2c4232220e563d04701f5f44607

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

The original Linux kernel CVE announcement for CVE-2026-72224 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72224

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:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.4

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: 0
  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).