[CVE-2026-23032][LOW] null_blk: fix kmemleak by releasing references to fault configfs items

[CVE-2026-23032][LOW] null_blk: fix kmemleak by releasing references to fault configfs items

[AL-KERNEL]

CVE: CVE-2026-23032
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: null_blk: fix kmemleak by releasing references to fault configfs items
Commit: 1a3286edf4d48ce37f8982ff3c3b65159a5ecbb2
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1a3286edf4d48ce37f8982ff3c3b65159a5ecbb2
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-23032
Analysis date: Sun, 20 Sep 2026 00:12:15 -0400
ActionableScore: 1
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-2026-23032 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-23032

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-2026-23032	LOW	https://www.kernelcve.org/list/?q=CVE-2026-23032 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 'A memory leak in the null_blk fault injection configfs cleanup path occurs because references to timeout_inject, requeue_inject, and init_hctx_fault_inject items are not released when a nullb device is removed. Repeated creation and removal of null_blk devices can accumulate leaked configfs objects and may eventually cause memory exhaustion. For the CVSS the PR:H is used because creating and removing null_blk configfs devices normally requires administrative control over configfs and the block device configuration. The issue is local and is not network reachable. Impact is denial of service through resource exhaustion only. The patch context does not indicate a use after free, out of bounds access, information disclosure, integrity impact, or privilege escalation primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) 	MAYBE	INIT LEAK HARDWARE 	-	-	checked

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

ActionableScore=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: 1
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate**::

No floor or cap was applied. The patch establishes a concrete persistent reference leak, but does not establish host-wide exhaustion, a crash, memory corruption, authorization bypass, or a non-DoS security consequence.

2. Signal breakdown

* +1 Concrete persistent kernel resource/reference leak. The three fault-injection configfs child items receive references when added as default groups, and the old removal path does not call config_item_put for them. The references and associated allocations remain leaked after removal of the top-level nullb configfs group.
* +0 Resource exhaustion impact. Repeated create and remove activity can accumulate leaked objects, but supplied evidence does not establish the number of reachable cycles, host-wide exhaustion, cgroup or namespace-accounting bypass, or a reliable immediate DoS.
* +0 Memory corruption. No use-after-free, double put, stale dereference, out-of-bounds access, invalid refcount decrement, or active-object corruption is established.
* +0 Reliable kernel crash. The demonstrated symptom is kmemleak reporting an unreferenced object, not a crash or kernel fault.
* +0 Confidentiality and integrity impact. No information disclosure, unauthorized modification, ownership violation, or privilege-escalation primitive is established.
* +0 Local unprivileged trigger. The supplied patch does not establish that an ordinary unprivileged user can create and remove the required null_blk configfs objects.
* No privilege penalty applied. The supplied context suggests configfs and null_blk management, but does not positively establish that complete trigger execution requires host-admin-equivalent privilege. Therefore HostAdminRequired remains UNKNOWN rather than YES.
* No niche-subsystem penalty applied. null_blk fault injection is configuration-dependent, but the supplied evidence does not prove that an attacker cannot instantiate or reach the required path.

3. Reachability analysis

The affected path is local and requires the null_blk driver with CONFIG_BLK_DEV_NULL_BLK_FAULT_INJECTION enabled, configfs exposure, creation of a nullb device, and later removal of that device.

The visible input does not establish the exact access checks governing creation and deletion of the relevant configfs entries. In typical deployments these operations are administratively controlled, but this is not enough to mark HostAdminRequired as YES under the stated evidence rules.

There is no network trigger, special hardware requirement, race condition, firmware dependency, or prior privileged setup explicitly established by the patch. Namespace-scoped reachability is unresolved because the complete configfs and null_blk lifecycle operation is not shown to be available inside attacker-controlled namespaces.

4. Primitive and severity interpretation

The exact primitive is a missing release of three configfs item references during null_blk device teardown. This is a persistent resource and reference leak, not a dangling-reference use.

There is no active structured stale-object access, no object reuse, no second lifetime mutation on a potentially freed object, and no repeated release or refcount-underflow pattern. The added config_item_put calls are ordinary cleanup for references that were previously never released.

PrimitiveClass is NONE because the defect establishes a memory/resource leak only. The demonstrated consequence is bounded memory growth per create and remove cycle. Eventual resource exhaustion is plausible under sustained repeated use, but the supplied evidence does not establish a practical host-wide exhaustion condition or isolation-boundary bypass.

ImportantCandidate is NO because no kernel-corruption, lifetime, ownership, authorization, or semantic-reinterpretation primitive remains unresolved. AutoDowngradeAllowed is YES because the issue can be handled as a low-priority resource-leak correction unless deployment-specific evidence shows an attacker can perform very high-volume null_blk lifecycle operations.

Likely operational severity is Low to ordinary Moderate, depending on whether the affected test-oriented null_blk fault-injection configuration is enabled and exposed to an actor able to repeatedly create and remove devices.

5. One-sentence report phrase

A missing config_item_put cleanup in the null_blk fault injection configfs removal path leaks references during repeated nullb device deletion and may eventually cause local resource exhaustion.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

The patch establishes a straightforward resource/reference leak without a demonstrated memory-corruption, privilege-escalation, confidentiality, integrity, or security-boundary primitive.

7. Call-site confidence

Call-site confidence: high

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

Patch: null_blk: fix kmemleak by releasing references to fault configfs items
Commit: 1a3286edf4d48ce37f8982ff3c3b65159a5ecbb2
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1a3286edf4d48ce37f8982ff3c3b65159a5ecbb2

Commit description:

When CONFIG_BLK_DEV_NULL_BLK_FAULT_INJECTION is enabled, the null-blk
driver sets up fault injection support by creating the timeout_inject,
requeue_inject, and init_hctx_fault_inject configfs items as children
of the top-level nullbX configfs group.

However, when the nullbX device is removed, the references taken to
these fault-config configfs items are not released. As a result,
kmemleak reports a memory leak, for example:

unreferenced object 0xc00000021ff25c40 (size 32):
  comm "mkdir", pid 10665, jiffies 4322121578
  hex dump (first 32 bytes):
    69 6e 69 74 5f 68 63 74 78 5f 66 61 75 6c 74 5f  init_hctx_fault_
    69 6e 6a 65 63 74 00 88 00 00 00 00 00 00 00 00  inject..........
  backtrace (crc 1a018c86):
    __kmalloc_node_track_caller_noprof+0x494/0xbd8
    kvasprintf+0x74/0xf4
    config_item_set_name+0xf0/0x104
    config_group_init_type_name+0x48/0xfc
    fault_config_init+0x48/0xf0
    0xc0080000180559e4
    configfs_mkdir+0x304/0x814
    vfs_mkdir+0x49c/0x604
    do_mkdirat+0x314/0x3d0
    sys_mkdir+0xa0/0xd8
    system_call_exception+0x1b0/0x4f0
    system_call_vectored_common+0x15c/0x2ec

Fix this by explicitly releasing the references to the fault-config
configfs items when dropping the reference to the top-level nullbX
configfs group.

Cc: stable@vger.kernel.org
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Fixes: bb4c19e ("block: null_blk: make fault-injection dynamically configurable per device")
Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  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=1a3286edf4d48ce37f8982ff3c3b65159a5ecbb2

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

The original Linux kernel CVE announcement for CVE-2026-23032 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-23032

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: 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).