[CVE-2026-72223][LOW] nvdimm/btt: Free arena sub-allocations on discover_arenas() error path

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

CVE: CVE-2026-72223
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: nvdimm/btt: Free arena sub-allocations on discover_arenas() error path
Commit: 2d0364937550a7b3e2592629c2a68753ac020b28
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2d0364937550a7b3e2592629c2a68753ac020b28
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72223
Analysis date: Sat, 15 Aug 2026 12:01:03 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
Missing cleanup in the NVDIMM/BTT discover_arenas() error path can leak arena sub-allocations during failed discovery, but triggering is local, privileged, hardware-specific, and limited to potential resource exhaustion.

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

The original Linux kernel CVE announcement for CVE-2026-72223 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72223

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-72223	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 arena discovery can leak kernel memory on some discover_arenas error paths because sub allocations created for the freelist, rtt, and map_locks are not released before the arena object is freed. The issue is local and depends on NVDIMM/BTT device discovery or reconfiguration reaching a failing discovery path, so it is not directly network reachable. For the CVSS the PR:H is used because reliable triggering normally requires administrator level control over persistent memory namespace or BTT device management. Impact is denial of service through gradual resource exhaustion if the failing discovery path can be repeated. No UAF, OOB access, information leak, or privilege escalation primitive is indicated by the code change.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 0)	YES	LEAK ERRORPATH UAF MEMORY  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=0

## 1. ActionableScore

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

## 2. Signal breakdown

Triggered signals:

* Important filesystem/storage path: +1
  NVDIMM/BTT is a storage-related subsystem, but the affected path is arena discovery error handling, not a normal data I/O or metadata update path.

* Availability impact realistic: +1 in the paranoid interpretation only
  Repeated failing discovery attempts could theoretically accumulate leaked memory and cause resource exhaustion.

Subtracting signals:

* Requires admin/root/CAP_* in typical deployments: -2
  Reliable triggering normally requires control over NVDIMM/BTT namespace or persistent-memory device configuration.

* Rare hardware/configuration-dependent path: -1
  This depends on NVDIMM persistent memory and BTT arena discovery failure paths, which are not common default attack surfaces.

Not triggered:

* No memory corruption primitive.
  The patch adds missing kfree() calls for arena->freelist, arena->rtt, and arena->map_locks.

* No UAF, double free, OOB write, page-cache corruption, stale pointer reuse, or privilege escalation primitive is shown.

* No remote reachability.

## 3. Reachability analysis

The bug is local and depends on NVDIMM/BTT device discovery or reconfiguration reaching an error path in discover_arenas(). In typical deployments, this requires administrator-level control over persistent memory namespaces or related storage device management. Containers or namespaces usually do not expose this path to unprivileged users unless the host deliberately delegates such device-management capabilities. The affected configuration is hardware and subsystem specific, so broad default exposure is low.

## 4. Severity interpretation

This behaves like a low-priority resource leak rather than an Important-class kernel vulnerability. The realistic impact is gradual kernel memory leakage during repeated failed arena discovery, with possible DoS only if an already privileged actor can repeatedly trigger the failing path. There is no evidence of memory corruption, confidentiality impact, integrity impact, or privilege escalation.

## 5. One-sentence report phrase

Missing cleanup in the NVDIMM/BTT discover_arenas() error path can leak arena sub-allocations during failed discovery, but triggering is local, privileged, hardware-specific, and limited to potential resource exhaustion.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This can be auto-closed for urgent security triage because it is a privileged, rare-configuration memory leak with no concrete corruption or privilege-escalation primitive.

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

Patch: nvdimm/btt: Free arena sub-allocations on discover_arenas() error path
Commit: 2d0364937550a7b3e2592629c2a68753ac020b28
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2d0364937550a7b3e2592629c2a68753ac020b28

Commit description:

Memory allocated by btt_freelist_init(), btt_rtt_init(), and
btt_maplocks_init() is not freed on some discover_arenas() error
paths. This leaks memory when arena discovery fails.

Add the missing kfree() calls to release the allocations before
returning an error.

[ 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-v1-1-592300fb7a43@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=2d0364937550a7b3e2592629c2a68753ac020b28

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

The original Linux kernel CVE announcement for CVE-2026-72223 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72223

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: 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).