[CVE-2026-72099][MODERATE REGULAR] dm-integrity: don't increment hash_offset twice commit edf025f083854f80032b73a1aad69a3c90db236f upstream.

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

CVE: CVE-2026-72099
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: dm-integrity: don't increment hash_offset twice commit edf025f083854f80032b73a1aad69a3c90db236f upstream.
Commit: cf9feed8c131e303ecf2afebe6f791be018818ad
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cf9feed8c131e303ecf2afebe6f791be018818ad
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72099
Analysis date: Sun, 16 Aug 2026 03:25:44 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline, manual review recommended
Manual review required: YES

Summary:
dm-integrity may advance hash_offset twice for non power of two tag_size values in the discard metadata path, which can corrupt integrity tag accounting and cause local data integrity failures or storage availability impact on affected configured volumes.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-72099 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72099

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
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CVE-2026-72099	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:L/A:H';CWE-682;CWE-693;CWE-754;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:L';BEST CVSS score: '5.3';DESCR 'dm-integrity incorrectly advances hash_offset twice for non power of two tag_size values in the discard related metadata path. This can make integrity metadata accounting drift from the intended tag position and can cause wrong tags to be used or stored for affected sectors. The realistic impact is local data integrity failure and I/O errors rather than code execution. For the CVSS the PR:L is used for the paranoid score because an unprivileged local process may be able to trigger filesystem writes or discard activity on an already configured dm-integrity volume, although creating or changing the device mapping normally requires administrator privileges. The issue is not network reachable. Impact is at least local denial of service or data integrity degradation on the affected volume, and the paranoid score keeps higher availability impact for storage level failure without treating this as memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 4)  SKIP CVE-2026-72099 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: 84597a44a9d86ac949900441cea7da0af0f2f473 YES  NO NO unknown 	MAYBE	DISK LINUS  INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=4
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 4
* Final recommended bucket: **Borderline, manual review recommended**

## 2. Signal breakdown

Paranoid score signals:

* Local unprivileged trigger: +1. If a dm-integrity volume is already configured with discard support, ordinary local filesystem activity may indirectly cause discard related metadata handling, depending on mount and filesystem behavior.
* Filesystem/storage metadata corruption reachable by a local user: +1. The bug affects integrity tag offset accounting and may cause wrong integrity metadata to be used or stored.
* Important filesystem/storage path: +1. dm-integrity is a block layer integrity feature and incorrect metadata accounting can affect stored data reliability.
* Integrity impact plausible: +1. Incorrect hash_offset handling can plausibly cause integrity tag mismatch, wrong tag placement, or data integrity degradation.
* Availability impact realistic: +1. Resulting integrity failures or I/O errors may make affected storage ranges or volumes unreliable.
* Rare AND difficult-to-reach configuration: -1. The issue requires dm-integrity discard support and a non power of two tag_size, which is not a common default deployment.
* Corruption primitive highly constrained or metadata-only: -1. The patch shows an arithmetic/bookkeeping bug, not UAF, OOB write, arbitrary write, or attacker-controlled kernel memory corruption.

Conservative score omits the local unprivileged trigger assumption where discard activity is admin controlled, giving 3.

## 3. Reachability analysis

The affected path is local storage/block-layer handling, not network reachable. Creating or configuring the dm-integrity mapping normally requires administrator privileges, but triggering the faulty path may be possible by local users on an already configured volume if filesystem operations or mounted discard behavior reach this code. Containers and namespaces do not generally make dm-integrity setup unprivileged, but delegated storage access could expose the runtime trigger surface. Practical exploitation depends on a specific dm-integrity configuration with optional discard support and non power of two tag_size.

Call-site confidence: medium. The patch is small and localized, but the function context indicates metadata offset calculation in a storage integrity path.

## 4. Severity interpretation

This behaves more like a borderline actionable Moderate storage integrity issue than an Important-class kernel memory corruption bug. The theoretical risk is data integrity degradation or volume-level availability impact, not privilege escalation. The patch does not support UAF, double-free, OOB write, arbitrary write, page-cache corruption, or Dirty-Pipe-like ownership bypass. Manual review is still justified because filesystem and block integrity metadata bugs can have persistent operational impact even without kernel code execution.

## 5. One-sentence report phrase

dm-integrity may advance hash_offset twice for non power of two tag_size values in the discard metadata path, which can corrupt integrity tag accounting and cause local data integrity failures or storage availability impact on affected configured volumes.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Manual review is recommended because the bug affects storage integrity metadata and may cause persistent data integrity or availability problems, but the patch does not show a concrete memory corruption or privilege escalation primitive.

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

Patch: dm-integrity: don't increment hash_offset twice commit edf025f083854f80032b73a1aad69a3c90db236f upstream.
Commit: cf9feed8c131e303ecf2afebe6f791be018818ad
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cf9feed8c131e303ecf2afebe6f791be018818ad

Commit description:

hash_offset is already incremented in the loop "for (i = 0; i < to_copy;
i++, ts--)". Do not increment it again.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Assisted-by: Claude:claude-opus-4.6
Fixes: 84597a44a9d8 ("dm-integrity: dm integrity: add optional discard support")
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat -rw-r--r-- drivers/md/dm-integrity.c 3

Changed files:
  drivers/md/dm-integrity.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=cf9feed8c131e303ecf2afebe6f791be018818ad

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

The original Linux kernel CVE announcement for CVE-2026-72099 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72099

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:L/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:H
  The Best / paranoid CVSS score: 5.3

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: 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).