[CVE-2026-46045][MODERATE 7.0] md/md-llbitmap: skip reading rdevs that are not in_sync

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

CVE: CVE-2026-46045
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: md/md-llbitmap: skip reading rdevs that are not in_sync
Commit: 98623c7e2a51eab1833c8628d33fa9c6ef3ce325
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=98623c7e2a51eab1833c8628d33fa9c6ef3ce325
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46045
Analysis date: Wed, 27 May 2026 15:29:06 -0400
ActionableScore: 6
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-46045 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46045

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 7.0
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
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CVE-2026-46045	MODERATE	CHECK	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:H/A:H';*CWE-20;CWE-754;CWE-345;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:H/A:H';BEST CVSS score: '6.3';DESCR 'md llbitmap can read bitmap pages from a spare or rebuilding rdev that is not In_sync, so stale or uninitialized bitmap data may be trusted for dirty bit tracking. This can cause incorrect recovery decisions and persistent data corruption during rebuild or normal md operation. For the CVSS the PR:L is used in the paranoid score because a local user may exercise filesystem or block workload while an already configured md array is rebuilding, even though creating that array state usually requires administrator control. The issue is not network reachable and does not provide a kernel memory corruption primitive. Impact is storage integrity loss and possible availability loss due to corrupted array data.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)  SKIP CVE-2026-46045  SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	READ DANGER DISK SIMPLEFIX IMPROVEONLY LINUS KPANIC 	-	-	checked

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

ActionableScore=6
ActionableScoreLower=3

1. ActionableScore
* Conservative score: 3
* Paranoid score: 6
* Final recommended bucket: **Actionable Moderate at minimum**::

2. Signal breakdown
* Important filesystem/storage path: +1. The bug affects md RAID bitmap handling, recovery, and dirty bit tracking.
* Integrity impact plausible: +1. Stale or uninitialized bitmap data can cause incorrect dirty tracking and persistent data corruption.
* Availability impact realistic: +1. Corrupted recovery state can make array data unreliable or require administrative recovery.
* Local unprivileged trigger in paranoid interpretation: +1. A local user may generate block or filesystem workload while an already configured md array is rebuilding.
* Filesystem/storage metadata corruption reachable by local workload in paranoid interpretation: +1. The dirty bitmap is storage recovery metadata and can influence which blocks are recovered or skipped.
* Broad storage exposure in paranoid interpretation: +1. md RAID is a common Linux storage subsystem, even if this exact llbitmap and rebuild condition is configuration-dependent.
* Requires admin/root for conservative interpretation: -2. Creating the md array state, adding spare devices, and starting rebuild normally require administrative privileges.
* No kernel memory corruption signal. The patch does not indicate UAF, OOB write, arbitrary write, refcount takeover, or privilege escalation.

3. Reachability analysis
The vulnerable path is reached when md llbitmap reads bitmap pages during RAID operation or recovery and selects an rdev that is assigned and not Faulty but not In_sync. In conservative terms, reliable setup requires administrator control over md RAID configuration and rebuild state. In a more practical paranoid scenario, once the array is already configured and rebuilding, ordinary local workloads using the filesystem or block device may influence timing and make the bad bitmap state security relevant. The issue is not network reachable and namespaces do not usually lower the privilege needed to manage md arrays.

4. Severity interpretation
This is not a kernel memory corruption or LPE issue. It is a storage integrity bug with possible persistent data corruption, which is more actionable than an ordinary crash-only Moderate. The conservative view is a privileged recovery-state bug, but the paranoid view should not be auto-closed because stale bitmap data can affect recovery correctness and corrupt user data.

5. One-sentence report phrase
md llbitmap may read dirty bitmap data from a spare or rebuilding rdev that is not In_sync, causing incorrect recovery tracking and possible persistent data corruption during md RAID operation.

6. Manual review recommendation
MANUAL CHECK REQUIRED. Persistent storage integrity impact in md RAID recovery should be reviewed manually even without kernel memory corruption or privilege escalation.

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

Patch: md/md-llbitmap: skip reading rdevs that are not in_sync
Commit: 98623c7e2a51eab1833c8628d33fa9c6ef3ce325
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=98623c7e2a51eab1833c8628d33fa9c6ef3ce325

Commit description:

When reading bitmap pages from member disks, the code iterates through
all rdevs and attempts to read from the first available one. However,
it only checks for raid_disk assignment and Faulty flag, missing the
In_sync flag check.

This can cause bitmap data to be read from spare disks that are still
being rebuilt and don't have valid bitmap information yet. Reading
stale or uninitialized bitmap data from such disks can lead to
incorrect dirty bit tracking, potentially causing data corruption
during recovery or normal operation.

Add the In_sync flag check to ensure bitmap pages are only read from
fully synchronized member disks that have valid bitmap data.

Cc: stable@vger.kernel.org
Fixes: 5ab829f ("md/md-llbitmap: introduce new lockless bitmap")
Link: https://lore.kernel.org/linux-raid/20260223024038.3084853-2-yukuai@fnnas.com
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/md/md-llbitmap.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=98623c7e2a51eab1833c8628d33fa9c6ef3ce325

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

The original Linux kernel CVE announcement for CVE-2026-46045 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46045

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:H/UI:N/S:U/C:N/I:H/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:H
  The Best / paranoid CVSS score: 6.3

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: 6

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: YES
Published priority for this report (same as in Subject): MODERATE 7.0

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).