[CVE-2026-72440][MODERATE REGULAR] md/raid1: fix writes_pending and barrier reference leaks on write failures [ Upstream

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

CVE: CVE-2026-72440
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: md/raid1: fix writes_pending and barrier reference leaks on write failures [ Upstream
Commit: bffbbfcbd9393e315a7a4286dcd70e875265db9a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bffbbfcbd9393e315a7a4286dcd70e875265db9a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72440
Analysis date: Sat, 15 Aug 2026 22:26:05 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline manual review recommended. Not an Important candidate
Manual review required: YES

Summary:
md/raid1 write failure paths could leak `writes_pending` and barrier references, allowing a local writer under specific failure conditions to leave the array in an unbalanced state and cause storage availability degradation or hangs.

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

The original Linux kernel CVE announcement for CVE-2026-72440 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72440

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: YES

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

======================================================================
AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-72440	MODERATE	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:L/UI:N/S:U/C:N/I:N/A:H';*CWE-772;CWE-911;**CWE-400;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'md raid1 write error handling can leak internal accounting references when raid1_write_request completes a failed bio without reaching the normal write completion path. The leaked writes_pending reference and the missing barrier release can leave the array with unbalanced state and may cause later operations to wait indefinitely or stall storage recovery and write processing. For the CVSS the PR:L is used because a local user or process that can issue writes to a filesystem backed by the md raid1 device may be able to reach the affected path, although reliable triggering depends on RAID1 state, write failure handling, NOWAIT behavior, or blocked rdev conditions. The issue is not network reachable and is triggered through local block I/O paths rather than remote packet input. Impact is denial of service through storage hang or degraded availability. There is no concrete UAF, OOB access, information leak, or arbitrary write primitive visible from the patch, so confidentiality and integrity remain N for both base and paranoid scoring.';NO MANUAL CHECK; ,and ActionableScore result is Borderline manual review recommended. Not an Important candidate (with actual score 4)	YES	DISK SIMPLEFIX LEAK LINUS  INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	YES	NO	checked

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

ActionableScore=4
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: **3**
* Paranoid score: **4**
* Final recommended bucket: **Borderline manual review recommended. Not an Important candidate**::

## 2. Signal breakdown

Triggered signals:

* **Local unprivileged trigger: +1**
  A local user or process that can issue writes to a filesystem or block device backed by md/raid1 may reach `raid1_make_request()`.

* **Reliable kernel crash / strong DoS: +1**
  Not a crash primitive, but leaked `writes_pending` and barrier references can leave md/raid1 accounting unbalanced and cause later writes, freeze, recovery, or barrier waits to stall.

* **Important filesystem/storage path: +1**
  This is in the md/raid1 write path, affecting block-layer storage availability.

* **Availability impact realistic: +1**
  Paranoid-only. The impact can persist as a storage hang or blocked array state, not just a failed single write.

Subtracted signals:

* **Hard or unreliable trigger / special conditions required: -1**
  The bug depends on write failure paths such as `REQ_NOWAIT`, `wait_barrier()` failure, `wait_blocked_rdev()` failure, clustered/resync states, or error handling paths. Ordinary successful writes do not trigger it.

Not triggered:

* No remote reachability.
* No generic memory corruption.
* No UAF, OOB access, double-free, arbitrary write, page-cache corruption, or Dirty-Pipe-like ownership bypass.
* No plausible privilege escalation primitive from the patch.
* No confidentiality or integrity impact supported by the diff.

Call-site confidence: **high**, because the caller `raid1_make_request()` and the changed callee `raid1_write_request()` are both visible in the supplied patch.

## 3. Reachability analysis

The bug is locally reachable through writes to an md/raid1-backed block device or filesystem. In typical deployments, ordinary users may indirectly issue such writes through a mounted filesystem, but reliable triggering requires specific failure or blocked-device conditions rather than normal I/O.

Namespaces and containers do not automatically make this remotely reachable. A containerized process with write access to storage backed by the affected md/raid1 device could contribute to triggering the path, but controlling md failure states or blocked rdev conditions usually requires additional environmental factors or administrative setup.

The path is common for systems using md/raid1, but md/raid1 itself is deployment-dependent. The issue is not packet-triggerable and has no realistic network vector.

## 4. Severity interpretation

This behaves like a **borderline Moderate storage availability issue**, not an Important-class kernel vulnerability.

The realistic impact is local denial of service through storage stalls or md/raid1 accounting deadlock. The patch fixes reference/accounting leaks, not memory lifetime corruption. There is no evidence of attacker-controlled object reuse, stale pointer dereference, write-after-free, type confusion, arbitrary write, information disclosure, or privilege escalation.

The paranoid score is slightly higher because storage hangs can be operationally significant and md/raid1 is an important storage path, but the bug should remain below Important severity without a concrete corruption or privilege boundary bypass primitive.

## 5. One-sentence report phrase

md/raid1 write failure paths could leak `writes_pending` and barrier references, allowing a local writer under specific failure conditions to leave the array in an unbalanced state and cause storage availability degradation or hangs.

## 6. Manual review recommendation

**MANUAL CHECK RECOMMENDED**

Reason: the issue is not memory corruption and is likely DoS-only, but it affects an important storage write path and can cause persistent md/raid1 availability problems under failure conditions. It does not require urgent Important-class handling based on the supplied patch.

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

Patch: md/raid1: fix writes_pending and barrier reference leaks on write failures [ Upstream
Commit: bffbbfcbd9393e315a7a4286dcd70e875265db9a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bffbbfcbd9393e315a7a4286dcd70e875265db9a

Changed files:
  drivers/md/raid1.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=bffbbfcbd9393e315a7a4286dcd70e875265db9a

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

The original Linux kernel CVE announcement for CVE-2026-72440 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72440

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:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.5

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: 3
  Paranoid ActionableScore: 4

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).