[CVE-2026-72438][MODERATE REGULAR] md/raid10: fix writes_pending and barrier reference leaks on discard failures [ Upstream

[CVE-2026-72438][MODERATE REGULAR] md/raid10: fix writes_pending and barrier reference leaks on discard failures [ Upstream

[AL-KERNEL]

CVE: CVE-2026-72438
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: md/raid10: fix writes_pending and barrier reference leaks on discard failures [ Upstream
Commit: d1324b41dabd26787559efaeb430643c627c1eb0
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d1324b41dabd26787559efaeb430643c627c1eb0
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72438
Analysis date: Sun, 16 Aug 2026 02:36:36 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Ordinary Moderate / Low-like. Not an Actionable Moderate candidate
Manual review required: NO

Summary:
md raid10 discard error paths can leak writes_pending and barrier references, allowing a local discard workload under specific failure conditions to stall later array operations and cause an availability-only storage DoS.

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

The original Linux kernel CVE announcement for CVE-2026-72438 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72438

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: MODERATE REGULAR
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-2026-72438	MODERATE	CHECK WITH IMPACT FROM ORIG NN LOW	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-404;**CWE-400;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'md raid10 discard error paths can leak writes_pending references acquired by md_write_start() and can also leak a barrier reference after wait_barrier() succeeds and bio_split() fails. A local workload that can issue discard requests to an affected raid10 md device may leave write accounting or barrier state unbalanced, which can stall later writes or recovery operations and cause denial of service for the array. For the CVSS the PR:L is used because triggering requires local access able to generate discard I/O or influence a mounted filesystem that issues discard, while full administrator privileges are not always required in practical deployments. The issue is not network reachable. Impact is availability only. For the paranoid score, the highest still defensible interpretation is A:H for a stuck raid10 device, without confidentiality or integrity impact because the patch shows a reference leak and not a memory corruption primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like. Not an Actionable Moderate candidate (with actual score 3)	YES	DISK SIMPLEFIX LEAK LINUS  INCREASED_FROM_LOW_TO_MODERATE70_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN3 DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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

## 1. ActionableScore

ActionableScore=3
ActionableScoreLower=2

* Conservative score: 2
* Paranoid score: 3
* Final recommended bucket: **Ordinary Moderate / Low-like. Not an Actionable Moderate candidate**::

## 2. Signal breakdown

Conservative signals:

* Important filesystem/storage path: +1. The bug is in md/raid10 discard handling and can affect array write/barrier accounting.
* Availability impact realistic: +1. A leaked writes_pending or barrier reference can plausibly stall later writes, discard handling, or recovery for the affected array.
* Hard or unreliable trigger condition: -1. Triggering depends on discard failure paths, NOWAIT barrier failure, or bio_split allocation failure, not an ordinary successful I/O path.
* Reliable kernel crash / strong DoS: +1. Not a direct crash, but a persistent stuck accounting state can cause a strong storage DoS for the md raid10 device.

Paranoid additional interpretation:

* Local unprivileged trigger: +1. In some deployments, an unprivileged local workload may indirectly generate discard I/O through a mounted filesystem with discard behavior, although setting up md raid10 and discard policy is privileged.

Not applied:

* No memory corruption signal. The patch fixes missing md_write_end() and allow_barrier() calls, not UAF, OOB write, double free, type confusion, or arbitrary write.
* No privilege escalation plausible signal. There is no supported path to credential change, object replacement, or attacker-controlled memory corruption.
* No confidentiality or integrity impact. The effect is accounting/barrier reference leakage, not data disclosure or unauthorized modification.
* No remote/network signal. The path is local block I/O, not network reachable.

Call-site confidence: high, because the relevant caller relationship is described directly: raid10_make_request() acquires writes_pending before raid10_handle_discard(), and the patch fixes the failing return paths inside that function.

## 3. Reachability analysis

The bug is reachable through discard handling on an affected md raid10 device. Reliable triggering requires a raid10 array, discard I/O, and one of the specific failure paths: wait_barrier() failure with NOWAIT or bio_split() allocation failure after wait_barrier() succeeds.

Typical setup and device administration require root or storage-management privileges. However, once the filesystem and discard behavior are configured, an ordinary local user may be able to indirectly cause discard activity through file operations depending on filesystem and mount options. Namespaces and containers do not normally expose raw md device management, but a container or service with access to a mounted filesystem backed by raid10 may contribute workload that reaches the path.

The issue is not default network-exposed and does not cross a clear container or namespace security boundary by itself.

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like storage DoS issue, not an Important-class kernel vulnerability.

The theoretical impact is persistent availability degradation of the affected raid10 array due to leaked internal references. The realistic evidence does not show memory corruption, privilege escalation, data corruption, or information disclosure. The failure conditions are relatively narrow, so this should not be treated like an actionable Moderate unless a product has high reliance on md raid10 discard paths and evidence of easy triggering.

## 5. One-sentence report phrase

md raid10 discard error paths can leak writes_pending and barrier references, allowing a local discard workload under specific failure conditions to stall later array operations and cause an availability-only storage DoS.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This can be handled as an auto-closable low-priority Moderate in most environments because it is a local storage accounting/reference leak with no demonstrated memory corruption, no LPE path, no confidentiality or integrity impact, and no network reachability.

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

Patch: md/raid10: fix writes_pending and barrier reference leaks on discard failures [ Upstream
Commit: d1324b41dabd26787559efaeb430643c627c1eb0
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d1324b41dabd26787559efaeb430643c627c1eb0

Changed files:
  drivers/md/raid10.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=d1324b41dabd26787559efaeb430643c627c1eb0

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

The original Linux kernel CVE announcement for CVE-2026-72438 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72438

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:L/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: 2
  Paranoid ActionableScore: 3

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: MODERATE
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): MODERATE REGULAR

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).