[CVE-2026-64213][LOW] hwmon: (lm90) Add lock protection to lm90_alert [ Upstream

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

CVE: CVE-2026-64213
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: hwmon: (lm90) Add lock protection to lm90_alert [ Upstream
Commit: bed1fc32e0eb653806fa98afcf55f9a311fc4ce2
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bed1fc32e0eb653806fa98afcf55f9a311fc4ce2
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64213
Analysis date: Fri, 24 Jul 2026 13:04:29 -0400
ActionableScore: 2
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A missing hwmon_lock in lm90_alert() can race with local hwmon sysfs writes and re enable an active hardware alert line, causing an interrupt storm and local DoS on affected lm90 hardware.

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

The original Linux kernel CVE announcement for CVE-2026-64213 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64213

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
======================================================================

CVE-2026-64213	LOW	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-667;CWE-362;**CWE-400;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'lm90_alert() can race with hwmon sysfs write operations because the alert handler updates data config without holding hwmon_lock. A concurrent sysfs write may restore an older configuration value and unintentionally re enable the hardware alert line while the alarm condition is still active, causing an interrupt storm. For the CVSS the PR:L paranoid case assumes a local user or service has delegated write access to the relevant hwmon sysfs attributes rather than full administrator control. The issue is not network reachable and requires a local control path plus suitable lm90 hardware and an active alert condition. Impact is denial of service through interrupt storm or degraded system responsiveness, with no evidence of memory corruption or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)	YES	SIMPLEFIX HARDWARE 	NO	NO	checked

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

ActionableScore=2
ActionableScoreLower=0

## 1. ActionableScore

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

## 2. Signal breakdown

Conservative signals:

* Reliable kernel crash / strong DoS: +1. The commit describes an interrupt storm caused by re-enabling the alert line while the alarm is still active.
* Availability impact realistic: +0. Already covered by the DoS signal, and the impact depends on specific hardware alert behavior.
* Hard or unreliable race / special timing required: -1. The issue requires an SMBus alert to race with a sysfs write.
* Requires admin/root/CAP in typical deployments: -2. Writing hwmon sysfs configuration attributes is normally restricted to root or privileged management services.
* Rare hardware/configuration dependency: -1. The affected path requires an lm90-compatible device, SMBus alert handling, and the LM90_HAVE_BROKEN_ALERT condition.

Paranoid signals:

* Local delegated trigger: +1. If a local service or reduced-privilege user has delegated write access to relevant hwmon sysfs attributes, the practical PR can be lower than full root.
* Reliable kernel crash / strong DoS: +1. An interrupt storm can plausibly degrade or stall the system.
* Hard race / timing required: -1. Triggering still needs concurrency between alert handling and sysfs writes.
* Hardware/configuration dependency: -1. Requires suitable lm90 hardware and active alarm state.
* Net result is kept at 2 because this is DoS-only with no memory corruption, no UAF, no overwrite, no info leak, and no privilege escalation primitive.

## 3. Reachability analysis

The bug is local and hardware-dependent. A realistic trigger requires access to hwmon sysfs write operations while an lm90 alert condition is active. In typical deployments those writes require root or a privileged hardware-monitoring service, so the conservative interpretation treats the issue as privileged and low priority. Namespaces usually do not make physical hwmon sysfs controls available to ordinary container users unless explicitly passed through or delegated. The path is not network reachable.

Call-site confidence: high. The patch and commit directly identify the racing paths: lm90_alert() and sysfs write handlers such as lm90_write_convrate().

## 4. Severity interpretation

This behaves like a low-end Moderate or Low-like availability issue. The theoretical impact is an interrupt storm and degraded system responsiveness, but the patch does not show memory corruption, stale object lifetime, UAF, arbitrary write, object confusion, or a security-boundary bypass. Realistic exploitation requires special timing, specific hardware, an active alarm state, and write access to hwmon configuration.

## 5. One-sentence report phrase

A missing hwmon_lock in lm90_alert() can race with local hwmon sysfs writes and re enable an active hardware alert line, causing an interrupt storm and local DoS on affected lm90 hardware.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This is a race-triggered DoS-only issue with privileged or delegated local reachability, hardware dependency, and no evidence of memory corruption or privilege escalation.

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

Patch: hwmon: (lm90) Add lock protection to lm90_alert [ Upstream
Commit: bed1fc32e0eb653806fa98afcf55f9a311fc4ce2
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bed1fc32e0eb653806fa98afcf55f9a311fc4ce2

Changed files:
  drivers/hwmon/lm90.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=bed1fc32e0eb653806fa98afcf55f9a311fc4ce2

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

The original Linux kernel CVE announcement for CVE-2026-64213 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64213

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: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: 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).