[CVE-2026-46051][MODERATE REGULAR] md/raid5: fix soft lockup in retry_aligned_read()

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

CVE: CVE-2026-46051
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: md/raid5: fix soft lockup in retry_aligned_read()
Commit: 09880592f5a9dc73377d6eb5ac123537b5f8df49
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=09880592f5a9dc73377d6eb5ac123537b5f8df49
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46051
Analysis date: Wed, 27 May 2026 11:00:21 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Borderline, manual review recommended
Manual review required: YES

Summary:
A local RAID5 read workload can trigger an overlapped-stripe retry loop that prevents `handle_stripe()` from resolving the stripe, causing `raid5d` soft lockup and storage DoS without memory corruption.

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

The original Linux kernel CVE announcement for CVE-2026-46051 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46051

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.

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

CVE-2026-46051	MODERATE	CHECK	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-835;**CWE-400;CWE-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'A local denial of service can occur in md raid5 when retry_aligned_read() sees an overlapped stripe and releases it through the lockless released_stripes path. The stripe can be moved to handle_list and then taken again by retry_aligned_read() before handle_stripe() processes it, so the overlap is never resolved and raid5d can loop until a soft lockup occurs. For the CVSS the PR:L is used because a local user may be able to generate reads against an existing RAID5 backed filesystem, but reliable triggering depends on RAID5 layout, overlapping stripe state, and workload timing. The issue is not network reachable and does not involve UAF, out of bounds access, arbitrary write, information disclosure, or privilege escalation. Impact is denial of service only through a stuck raid5d path or system responsiveness loss.';NO MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 3)	YES	LOCK DEADLOCK DISK SIMPLEFIX LINUS  INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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

ActionableScore=3
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 3
* Final recommended bucket: **Borderline, manual review recommended**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1
  A local user may be able to generate read workloads against a filesystem or block device backed by an existing md RAID5 array.

* Important filesystem/storage path: +1
  md/raid5 is an important storage subsystem, and a stuck `raid5d` path can affect IO availability.

* Reliable kernel stall / strong DoS: +1
  The described failure mode is an infinite loop leading to soft lockup.

* Availability impact realistic: +1
  A stuck `raid5d` can degrade or block RAID5 IO and reduce system responsiveness.

Subtracting signals:

* Configuration-dependent exposure: -1
  Requires an md RAID5 array and the aligned-read path.

* Special workload/state condition: -1
  Requires an overlapped stripe and the specific ordering where `retry_aligned_read()` repeatedly removes the stripe before `handle_stripe()` resolves it.

Paranoid adjustment:

* Shared storage impact concern: +1
  On multi-user systems or storage appliances, local workloads may affect broader IO availability for other users or services, making this more actionable than a trivial per-process DoS.

No signals apply for memory corruption, UAF, OOB access, arbitrary write, information disclosure, privilege escalation, or remote reachability.

## 3. Reachability analysis

The trigger is local IO against an existing md RAID5 setup. A local user does not normally need administrative privileges to issue reads through a mounted filesystem, but the vulnerable path depends on system configuration and workload behavior.

Namespaces and containers may matter if untrusted workloads share storage backed by the affected RAID5 array. The issue is not network reachable by itself, though it can affect storage services that serve remote clients if their backend RAID5 device locks up.

## 4. Severity interpretation

This behaves like a local storage DoS issue, not an Important memory corruption issue. The patch fixes list/state handling around stripe release and processing, but it does not show UAF, OOB write, arbitrary write, or data corruption.

Realistic impact is raid5d soft lockup and IO availability loss. Theoretical escalation beyond DoS is not supported by the patch.

## 5. One-sentence report phrase

A local RAID5 read workload can trigger an overlapped-stripe retry loop that prevents `handle_stripe()` from resolving the stripe, causing `raid5d` soft lockup and storage DoS without memory corruption.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: no memory corruption or privilege escalation is shown, but the bug affects an important storage subsystem and can cause a system-level IO stall on shared RAID5 deployments.

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

Patch: md/raid5: fix soft lockup in retry_aligned_read()
Commit: 09880592f5a9dc73377d6eb5ac123537b5f8df49
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=09880592f5a9dc73377d6eb5ac123537b5f8df49

Commit description:

When retry_aligned_read() encounters an overlapped stripe, it releases
the stripe via raid5_release_stripe() which puts it on the lockless
released_stripes llist. In the next raid5d loop iteration,
release_stripe_list() drains the stripe onto handle_list (since
STRIPE_HANDLE is set by the original IO), but retry_aligned_read()
runs before handle_active_stripes() and removes the stripe from
handle_list via find_get_stripe() -> list_del_init(). This prevents
handle_stripe() from ever processing the stripe to resolve the
overlap, causing an infinite loop and soft lockup.

Fix this by using __release_stripe() with temp_inactive_list instead
of raid5_release_stripe() in the failure path, so the stripe does not
go through the released_stripes llist. This allows raid5d to break out
of its loop, and the overlap will be resolved when the stripe is
eventually processed by handle_stripe().

Fixes: 773ca82 ("raid5: make release_stripe lockless")
Cc: stable@vger.kernel.org
Signed-off-by: FengWei Shih <dannyshih@synology.com>
Signed-off-by: Chia-Ming Chang <chiamingc@synology.com>
Link: https://lore.kernel.org/linux-raid/20260402061406.455755-1-chiamingc@synology.com/
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/md/raid5.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=09880592f5a9dc73377d6eb5ac123537b5f8df49

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

The original Linux kernel CVE announcement for CVE-2026-46051 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46051

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: 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).