[CVE-2026-74372][MODERATE REGULAR] raid1: fix nr_pending leak in REQ_ATOMIC bad-block error path [ Upstream

[CVE-2026-74372][MODERATE REGULAR] raid1: fix nr_pending leak in REQ_ATOMIC bad-block error path [ Upstream

[AL-KERNEL]

CVE: CVE-2026-74372
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: raid1: fix nr_pending leak in REQ_ATOMIC bad-block error path [ Upstream
Commit: 5ac9e793ba2583d72740d929e7858a6c82e22ed5
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5ac9e793ba2583d72740d929e7858a6c82e22ed5
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74372
Analysis date: Sat, 15 Aug 2026 07:31:03 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Borderline Low Moderate. Not an Important candidate
Manual review required: NO

Summary:
A reference leak in the raid1 `REQ_ATOMIC` bad-block error path can leave `rdev->nr_pending` permanently elevated, preventing RAID device removal and causing a local storage-management denial of service.

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

The original Linux kernel CVE announcement for CVE-2026-74372 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74372

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-2026-74372	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-911;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 reference leak in the raid1 write path can occur when a REQ_ATOMIC write hits a bad-block range after rdev nr_pending has already been incremented for the current mirror. The error path skips the current mirror reference and leaves nr_pending permanently elevated, which can prevent the rdev from being removed from the RAID1 configuration. For the CVSS the PR:L is used because a local user or process must be able to submit writes that reach the affected md raid1 device, while reliable triggering also depends on REQ_ATOMIC support and a bad-block condition. The issue is not network reachable and does not indicate a use-after-free, out-of-bounds access, or arbitrary write primitive. Impact is denial of service for RAID device management, mainly blocked rdev removal or recovery operations, not privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Borderline Low Moderate. Not an Important candidate (with actual score 3)	YES	DISK SIMPLEFIX LEAK ERRORPATH LINUS  INCREASED_FROM_LOW_TO_MODERATE70_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN3 DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	YES	NO	checked

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

ActionableScore=3
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 3
* Final recommended bucket: **Borderline Low Moderate. Not an Important candidate**::

## 2. Signal breakdown

Triggered signals:

* Local unprivileged trigger: +1
  A local process may be able to submit writes that reach the affected md raid1 device, depending on filesystem, block device access, and atomic write support.

* Real lifetime corruption: +1
  This is a reference lifetime bug: `rdev->nr_pending` is incremented but not decremented on the `REQ_ATOMIC` bad-block error path.

* Availability impact realistic: +1
  The leaked pending reference can permanently prevent `rdev` removal because `raid1_remove_conf()` refuses removal while `nr_pending > 0`.

* Important filesystem/storage path: +1
  The bug is in md raid1 write handling and affects RAID device management and recovery/removal behavior.

Subtractors:

* Hard or special triggering conditions required: -1
  Triggering requires `REQ_ATOMIC` plus a bad-block range hit in the relevant mirror path.

* Rare/configuration-dependent condition: -1
  Atomic write support and the exact bad-block condition are not broad default everyday paths.

Conservative interpretation reduces the score to 2 because this is a reference leak/resource-management issue without memory corruption. Paranoid interpretation keeps 3 due to persistent RAID management availability impact.

## 3. Reachability analysis

The bug is locally reachable through writes to an md raid1 device when `REQ_ATOMIC` is used and the request intersects a bad-block range. It is not network reachable. Namespace or container impact depends on whether the container or delegated service can write to the affected block device or filesystem path that issues atomic writes. In typical deployments, direct RAID management is privileged, but the write path itself may be reachable by a local user with write access to storage backed by the md device.

The path is not a common default trigger because it depends on atomic write support and a bad-block condition.

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like storage availability issue, not an Important-class vulnerability. The patch shows a leaked pending reference, not UAF, OOB access, arbitrary write, page-cache corruption, or privilege escalation. The realistic impact is persistent inability to remove or recover an affected RAID member, not kernel code execution or data theft.

## 5. One-sentence report phrase

A reference leak in the raid1 `REQ_ATOMIC` bad-block error path can leave `rdev->nr_pending` permanently elevated, preventing RAID device removal and causing a local storage-management denial of service.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: the patch and commit describe a constrained reference leak with availability impact only. There is no supported memory corruption primitive, no network exposure, and no plausible privilege-escalation path.

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

Patch: raid1: fix nr_pending leak in REQ_ATOMIC bad-block error path [ Upstream
Commit: 5ac9e793ba2583d72740d929e7858a6c82e22ed5
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5ac9e793ba2583d72740d929e7858a6c82e22ed5

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=5ac9e793ba2583d72740d929e7858a6c82e22ed5

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

The original Linux kernel CVE announcement for CVE-2026-74372 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74372

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).