[CVE-2026-72155][LOW] mtd: spi-nor: swp: Improve locking user experience

[CVE-2026-72155][LOW] mtd: spi-nor: swp: Improve locking user experience

[AL-KERNEL]

CVE: CVE-2026-72155
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: mtd: spi-nor: swp: Improve locking user experience
Commit: 9a0d8dec3d11ca95d67537ea8fa6ee2730a5038a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9a0d8dec3d11ca95d67537ea8fa6ee2730a5038a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72155
Analysis date: Sat, 15 Aug 2026 22:34:33 -0400
ActionableScore: 2
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
An incorrect lock_len calculation in the SPI NOR unlock path can leave flash regions locked when a full unlock should occur, causing limited denial of service for flash management operations without evidence of memory corruption or privilege escalation.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-72155 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72155

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: LOW
Manual review required: NO

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-2026-72155	LOW	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:L';CWE-682;CWE-755;CWE-703;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '3.3';DESCR 'An incorrect calculation in the SPI NOR software protection unlock path can leave part of the flash locked when the user requests an unlock operation that should effectively unlock the whole device. This affects the control plane for MTD flash protection and can prevent expected write or update operations on the device. For the CVSS the PR:L is used only for the paranoid score because some deployments may delegate MTD device access to a service account or reduced capability operator. The realistic base case is PR:H because changing SPI NOR protection normally requires administrative control over the MTD device. The issue is not network reachable and there is no evidence of memory corruption, information disclosure, or privilege escalation. Impact is limited denial of service for flash management operations.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)	YES	LOCK SIMPLEFIX HARDWARE LINUS 	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=2
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**

## 2. Signal breakdown

Conservative signals:

* Availability impact realistic: +1. The bug can prevent an expected SPI NOR unlock operation and block flash update or write workflows.
* Requires admin/root/CAP_* in typical deployments: -2. Changing SPI NOR protection normally requires privileged access to the MTD device.
* Rare hardware/configuration condition: -1. This requires SPI NOR software protection, a relevant locked region layout, and a specific unlock request pattern.
* Floor at 0.

Paranoid signals:

* Local reduced-privilege trigger: +1. Some products may delegate MTD operations to an updater service account or reduced-capability operator rather than full host root.
* Availability impact realistic: +1. The practical effect is failure to unlock flash regions, which may disrupt firmware or storage-management workflows.
* Important storage/device-management path: +1. SPI NOR may store firmware or boot-critical data in embedded systems.
* Rare hardware/configuration condition: -1. Triggering depends on SPI NOR SWP and a specific top/bottom protection geometry.
* No memory corruption, no UAF, no OOB access, no privilege escalation primitive, no confidentiality impact, no integrity impact beyond the operation failing.

## 3. Reachability analysis

The bug is triggered through the SPI NOR software-protection unlock path. In normal deployments this is a local privileged device-management operation, usually requiring root or equivalent access to MTD controls. It is not network reachable. Containers and namespaces generally do not expose raw MTD flash controls unless the host explicitly delegates the device. Realistic exploitation conditions are narrow and operational: a user or updater attempts to unlock the currently locked first block or first few blocks, but the calculation leaves a positive locked length instead of unlocking the whole device.

## 4. Severity interpretation

This behaves like a Low or ordinary Moderate correctness issue, not an Important-class kernel vulnerability. The impact is a limited availability problem for flash management operations. There is no supported memory corruption, no ownership or COW bypass, no sensitive-object access, and no plausible LPE path from the patch context. The paranoid score only accounts for delegated updater accounts and firmware-management importance, not for kernel compromise.

## 5. One-sentence report phrase

An incorrect lock_len calculation in the SPI NOR unlock path can leave flash regions locked when a full unlock should occur, causing limited denial of service for flash management operations without evidence of memory corruption or privilege escalation.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This can be auto-closed for security triage unless the product treats SPI NOR lock state as a security boundary for secure boot, firmware rollback protection, or trusted update enforcement.

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

Patch: mtd: spi-nor: swp: Improve locking user experience
Commit: 9a0d8dec3d11ca95d67537ea8fa6ee2730a5038a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9a0d8dec3d11ca95d67537ea8fa6ee2730a5038a

Commit description:

In the case of the first block being locked (or the few first blocks),
if the user want to fully unlock the device it has two possibilities:
- either it asks to unlock the entire device, and this works;
- or it asks to unlock just the block(s) that are currently locked,
  which fails.

It fails because the conditions "can_be_top" and "can_be_bottom" are
true. Indeed, in this case, we unlock everything, so the TB bit does not
matter. However in the current implementation, use_top would be true (as
this is the favourite option) and lock_len, which in practice should be
reduced down to 0, is set to "nor->params->size - (ofs + len)" which is
a positive number. This is wrong.

An easy way is to simply add an extra condition. In the unlock() path,
if we can achieve the same result from both sides, it means we unlock
everything and lock_len must simply be 0. A comment is added to clarify
that logic.

Fixes: 3dd8012 ("mtd: spi-nor: add TB (Top/Bottom) protect support")
Cc: stable@kernel.org
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Michael Walle <mwalle@kernel.org>
Signed-off-by: Pratyush Yadav <pratyush@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/mtd/spi-nor/swp.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=9a0d8dec3d11ca95d67537ea8fa6ee2730a5038a

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

The original Linux kernel CVE announcement for CVE-2026-72155 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72155

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:L/PR:H/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS score: 3.3

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: 0
  Paranoid ActionableScore: 2

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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).