[CVE-2026-97582][MODERATE REGULAR] hwmon: (gpio-fan) Fix use-after-free in alarm work

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

CVE: CVE-2026-97582
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: hwmon: (gpio-fan) Fix use-after-free in alarm work
Commit: 9b12bd724db9db318e3a68be17693583dc29a066
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9b12bd724db9db318e3a68be17693583dc29a066
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97582
Analysis date: Fri, 25 Sep 2026 11:30:47 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-97582 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97582

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: NO

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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

CVE-2026-97582	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-97582 CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;*CWE-672;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A use after free can occur in the gpio-fan alarm path because fan_alarm_irq_handler queues alarm_work without ensuring that pending work is cancelled before driver resources are released during unbind. A GPIO alarm event can queue fan_alarm_notify and the worker may later dereference freed fan_data and hwmon device objects after the interrupt and device resources have been removed. This can cause a kernel crash and at minimum a local denial of service. For the CVSS the PR:L value is used for the paranoid score because some deployments may delegate device lifecycle operations to a reduced capability service account or similar local management context. Typical host driver unbind operations are more restrictive and support the base PR:H score. The issue is not network reachable. The use after free primitive provides a plausible but unproven path to confidentiality integrity and privilege impact. Manual review is required to assess object reuse and exploitability.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0)	YES	INIT UAF HARDWARE  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4	NO	NO	checked

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

ActionableScore=0
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=YES
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 0
* Conservative score: 0
* Raw paranoid score: 0
* Paranoid score: 0
* Final recommended bucket: **Ordinary Moderate**::

No floor applies because host-admin-equivalent privilege is positively required for the complete trigger. No paranoid increase is justified because the patch establishes a cleanup-time UAF, but not controlled reclaim, post-free attacker-controlled contents, a second refcount mutation, disclosure, arbitrary write, or privilege escalation.

2. Signal breakdown

* +2 Real UAF or active lifetime violation. `fan_alarm_irq_handler()` can queue `alarm_work`, and `fan_alarm_notify()` can dereference `fan_data` and its hwmon device after devres teardown releases both objects.
* -2 Full host-admin-equivalent privilege. The complete trigger requires unbinding the host platform driver through the host sysfs driver bind or unbind interface. This is an administrative device-lifecycle operation.
* +0 Reliable kernel crash or strong DoS. A stale dereference can plausibly cause an Oops, but the supplied evidence is static-analysis based and does not demonstrate a reproducible host crash.
* +0 Controlled reclaim or object replacement. No evidence shows that an attacker can reclaim `gpio_fan_data` storage with attacker-shaped data before `fan_alarm_notify()` runs.
* +0 Structured stale-object exploitation leverage. The stale access is an asynchronous teardown worker operating on a fixed driver context. No meaningful post-free field consumption, callback dispatch, pointer steering, or attacker-controlled replacement is established.
* +0 Concrete repeated release or refcount mutation. The worker dereferences stale objects, but the patch does not establish a second `put`, `free`, `release`, or refcount operation through the same dangling reference.
* +0 Local unprivileged trigger. Not established. The full operation includes host driver unbind.
* +0 Remote reachability. Not established. The GPIO alarm interrupt is hardware or platform mediated and is not a network input path.
* +0 hard race penalty. Not applied. Although workqueue timing is relevant, the supplied evidence does not establish a uniquely narrow or uncontrollable one-shot timing condition.
* +0 rare hardware penalty. Not applied. The path requires a configured gpio-fan alarm IRQ, but hardware specificity alone is insufficient to subtract points.

3. Reachability analysis

The relevant attacker model is a host administrator or an equivalently privileged local device-management process. Such an actor can unbind the gpio-fan platform driver while an alarm work item is pending.

The vulnerable path requires a gpio-fan device configured with an alarm GPIO interrupt. The alarm can be generated by a fan or external GPIO state, but the supplied patch does not establish that an ordinary local user can control that signal or initiate the required host-driver unbind operation.

The driver bind or unbind control path is host sysfs device management, not a namespace-scoped operation. A container network namespace, user namespace, or delegated `CAP_NET_ADMIN` does not provide the complete trigger sequence. Therefore, `NamespaceScopedPrivilege=NO`.

No network-triggerable path, prior remote setup, firmware compromise, or ordinary-user ioctl or sysfs interface is established by the supplied evidence.

4. Primitive and severity interpretation

The exact primitive is a real asynchronous use-after-free. A pending workqueue item retains a raw pointer to the fixed `gpio_fan_data` driver context and its hwmon device. Devres teardown can release those objects after disabling the IRQ but before pending work is cancelled. The worker may subsequently dereference the freed objects.

This is fixed stale driver storage used by a teardown-time workqueue callback. It is not an active-object reuse case with demonstrated attacker-controlled replacement, structured post-free processing, callback control, arbitrary read or write, disclosure, or a security-boundary bypass.

No concrete repeated lifetime operation exists. The patch does not show a first `put` followed by a second `put`, `kref_put`, `free`, or refcount decrement through the same dangling reference. Thus, the repeated-release exception and the ActionableScore floor of 5 do not apply.

The primitive is therefore `CLASS_B` because a genuine kernel lifetime violation exists. However, it is a constrained cleanup-time UAF with only a plausible crash consequence. Important-grade exploitation leverage is unresolved but not meaningfully supported by the available evidence. `ImportantCandidate=NO` and `AutoDowngradeAllowed=YES` are appropriate.

Operationally, this should be treated as a host-admin-triggerable kernel reliability defect. It should be fixed through normal kernel maintenance, but it does not require emergency Important-class handling without further evidence of below-admin reachability or post-free object reuse.

5. One-sentence report phrase

A pending gpio-fan alarm work item can dereference freed driver and hwmon objects during host driver unbind, causing a constrained local use-after-free with a plausible kernel crash but no demonstrated exploitation primitive beyond denial of service.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Confirm the permissions on the gpio-fan driver unbind interface in the evaluated product and inspect `fan_alarm_notify()` for any post-free callback, pointer traversal, or externally visible data path not present in the supplied patch.

7. Call-site confidence

Call-site confidence: medium

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

Patch: hwmon: (gpio-fan) Fix use-after-free in alarm work
Commit: 9b12bd724db9db318e3a68be17693583dc29a066
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9b12bd724db9db318e3a68be17693583dc29a066

Commit description:

fan_alarm_irq_handler() queues fan_data->alarm_work, but nothing
cancels it.  fan_alarm_notify() dereferences fan_data and its hwmon
device.  On unbind, devres frees the interrupt, which only waits for
the handler itself, and then releases the hwmon device and fan_data,
so a pending fan_alarm_notify() can run after those frees.

Replace INIT_WORK() with devm_work_autocancel(), registered before
devm_request_irq().  The devres cleanup then frees the interrupt
first, so no new work can be queued, and cancels the work while
fan_data and the hwmon device are still alive.

This issue was found by an in-house static analysis tool.

Fixes: d6fe136 ("hwmon: add generic GPIO fan driver")
Cc: stable@vger.kernel.org
Assisted-by: Codex:gpt-5.6
Signed-off-by: Fan Wu <fanwu01@zju.edu.cn>
Link: https://patch.msgid.link/20260819033317.446191-1-fanwu01@zju.edu.cn
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/hwmon/gpio-fan.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=9b12bd724db9db318e3a68be17693583dc29a066

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

The original Linux kernel CVE announcement for CVE-2026-97582 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97582

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:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 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: unknown
  Paranoid ActionableScore: 0

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).