[CVE-2026-72439][LOW] md/raid10: fix writes_pending leak on write request failures [ Upstream

[CVE-2026-72439][LOW] md/raid10: fix writes_pending leak on write request failures [ Upstream

[AL-KERNEL]

CVE: CVE-2026-72439
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: md/raid10: fix writes_pending leak on write request failures [ Upstream
Commit: f94031c94eaebe14a7c9e91720064de0c5a54a6c
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f94031c94eaebe14a7c9e91720064de0c5a54a6c
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72439
Analysis date: Sun, 16 Aug 2026 03:45:04 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: YES

Summary:
A writes_pending reference leak in md raid10 write failure paths can leave the array with a permanently elevated pending write count, causing later storage management or recovery operations to hang, with local availability impact only.

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

The original Linux kernel CVE announcement for CVE-2026-72439 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72439

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: YES

A detailed explanation of the methodology and priority rules is included
at the end of this message.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-72439	LOW	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-400;CWE-703;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'A writes_pending reference leak in md raid10 can occur because raid10_make_request() calls md_write_start before dispatching a write, but several raid10_write_request() failure paths complete the bio and return without the matching md_write_end. This can leave the array with a permanently elevated pending write count and may cause later operations that wait for writes to drain to hang. For the CVSS the PR:L is used because a local user or process generally needs write access to a filesystem or block path backed by the affected RAID10 device to trigger write submission. The issue is not network reachable and requires a specific md raid10 setup plus a write failure path, so AC:H is appropriate. Impact is denial of service through blocked array management or recovery related operations, with no concrete evidence of confidentiality or integrity impact.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)	YES	DISK SIMPLEFIX LEAK LINUS 	YES	NO	checked

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

ActionableScore=2

## 1. ActionableScore

* Conservative score: **2**
* Paranoid score: **2**
* Final recommended bucket: **Ordinary Moderate / Low-like**::

## 2. Signal breakdown

Triggered signals:

* **Local unprivileged trigger: +1**
  A local process with write access to a filesystem or block path backed by the affected md/raid10 device may submit writes that reach `raid10_make_request()`.

* **Availability impact realistic: +1**
  A leaked `writes_pending` reference can keep the md array in a state where later operations waiting for pending writes to drain may hang.

* **Important filesystem/storage path: +1**
  The bug is in md/raid10 write handling, which is a relevant storage availability path.

Negative signals:

* **Hard or unreliable trigger / special failure path required: -1**
  The bug requires a write failure path such as `REQ_NOWAIT` would-block handling or another failed write queueing case. Normal successful writes do not trigger it.

Not awarded:

* **No generic memory corruption**
  This is a reference/counting leak, not UAF, OOB, double-free, arbitrary write, or type confusion.

* **No privilege escalation plausible**
  The patch does not show a corruption primitive, attacker-controlled reclaim, stale object reuse, or write primitive.

* **No confidentiality or integrity impact**
  The failure mode is blocked accounting state and potential hang, not data disclosure or unauthorized modification.

## 3. Reachability analysis

The likely trigger is local write submission to an md/raid10-backed device. In typical deployments, an unprivileged user may be able to write through a mounted filesystem, but reliably reaching the specific failure paths is not guaranteed. Direct block-device access or array management remains privileged.

Namespaces and containers do not materially improve reachability unless the container is explicitly given access to the md-backed storage path. The vulnerable code is not network reachable. The affected subsystem is not present on every system, but md/raid10 is a normal Linux storage configuration and not an exotic debug-only feature.

Call-site confidence: **high**, because the patch includes the relevant caller chain from `raid10_make_request()` to `__make_request()` and `raid10_write_request()`.

## 4. Severity interpretation

This behaves like an **ordinary Moderate / Low-like availability issue**, not an Important-class kernel vulnerability. The practical impact is a persistent `writes_pending` accounting leak that can cause hangs in later md operations. There is no evidence of memory corruption, privilege escalation, information disclosure, or persistent filesystem metadata corruption.

The theoretical worst case is stronger DoS if the leaked counter blocks important array management or recovery operations, but the trigger depends on specific write failure paths and does not justify Actionable Moderate escalation.

## 5. One-sentence report phrase

A writes_pending reference leak in md raid10 write failure paths can leave the array with a permanently elevated pending write count, causing later storage management or recovery operations to hang, with local availability impact only.

## 6. Manual review recommendation

**NO MANUAL CHECK NEEDED. NO MANUAL CHECK REQUIRED COULD BE AUTOCLOSED**

This is a storage-path reference leak with DoS-only impact, no memory corruption primitive, no network reachability, and no plausible privilege-escalation path shown by the patch.

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

Patch: md/raid10: fix writes_pending leak on write request failures [ Upstream
Commit: f94031c94eaebe14a7c9e91720064de0c5a54a6c
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f94031c94eaebe14a7c9e91720064de0c5a54a6c

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=f94031c94eaebe14a7c9e91720064de0c5a54a6c

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

The original Linux kernel CVE announcement for CVE-2026-72439 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72439

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: unknown
  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).