[CVE-2026-74733][LOW] gpio: pca953x: fix pca953x_irq_bus_sync_unlock regmap lock [ Upstream

[CVE-2026-74733][LOW] gpio: pca953x: fix pca953x_irq_bus_sync_unlock regmap lock [ Upstream

[AL-KERNEL]

CVE: CVE-2026-74733
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: gpio: pca953x: fix pca953x_irq_bus_sync_unlock regmap lock [ Upstream
Commit: e6a2f5f845f50b0c4299bace5111f56d3390a090
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e6a2f5f845f50b0c4299bace5111f56d3390a090
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74733
Analysis date: Sat, 22 Aug 2026 13:48:16 -0400
ActionableScore: 2
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A locking race in pca953x_irq_bus_sync_unlock() may allow concurrent GPIO or IRQ configuration to access regmap without i2c_lock, causing incorrect GPIO expander register reads or writes and possible local hardware or interrupt malfunction.

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

The original Linux kernel CVE announcement for CVE-2026-74733 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74733

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.

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

CVE-2026-74733	LOW	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:N/I:L/A:H';CWE-362;CWE-667;CWE-662;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:L/A:L';BEST CVSS score: '5.3';DESCR 'pca953x_irq_bus_sync_unlock() can access regmap without holding the driver i2c_lock even though regmap locking is disabled for this driver. Concurrent GPIO or IRQ configuration can race and may cause an incorrect hardware register to be read or written, leading to wrong GPIO direction or interrupt mask state. For the CVSS the PR:L value is used for the paranoid interpretation because some deployments may delegate gpiochip access or GPIO control to a local service or non-root user. The issue is not network reachable and requires local control over the affected GPIO expander configuration path. Impact is mainly integrity and availability of the attached hardware or interrupt handling, not kernel memory corruption or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)	YES	READ SIMPLEFIX RACE LINUS  DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS_AND_CIANNH INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	YES	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:

* Integrity impact plausible: +1. The race may cause an incorrect GPIO expander register to be read or written, affecting GPIO direction or interrupt mask state.
* Availability impact realistic: +1. Incorrect GPIO or IRQ configuration may break attached hardware behavior or interrupt handling.
* Hard or unreliable race / special timing required: -1. The issue requires concurrent GPIO or IRQ configuration paths to interleave incorrectly.
* Requires admin/root/CAP_* in typical deployments: -2. GPIO IRQ configuration and driver level control are normally restricted to privileged kernel or administrator controlled paths.

Conservative total is clamped to 0.

Paranoid signals:

* Local unprivileged trigger: +1. Some systems may delegate gpiochip access or GPIO control to a local service or non-root user.
* Integrity impact plausible: +1. Incorrect hardware register access can alter intended GPIO or IRQ state.
* Availability impact realistic: +1. Misconfigured interrupt or GPIO direction state can cause hardware level malfunction or local service disruption.
* Hard or unreliable race / special timing required: -1. Successful triggering depends on timing between concurrent operations.

Paranoid total: 2.

Not applied:

* No generic memory corruption. The patch shows incorrect regmap locking and wrong hardware register access, not UAF, OOB write, double free, type confusion, or refcount misuse.
* No privilege escalation plausible. There is no supported kernel memory corruption primitive or security boundary bypass.
* No remote reachable signal. The affected path is local GPIO or IRQ configuration, not packet or network input.
* No strong DoS signal. The expected impact is device or interrupt malfunction, not a demonstrated reliable kernel panic.

## 3. Reachability analysis

The bug is reachable through local GPIO expander configuration paths involving pca953x IRQ synchronization and direction setup. In typical deployments, changing GPIO direction or IRQ configuration is restricted to privileged users, kernel drivers, or administrator controlled services. Namespace or container delegation could lower practical privileges if a container or service is given access to gpiochip devices, but that is deployment specific. The path is not network reachable and requires affected PCA953x style GPIO expander hardware and concurrent operations.

Call-site confidence: high. The patch shows the affected function and the direct call path from pca953x_irq_bus_sync_unlock() to pca953x_gpio_direction_input_unlocked().

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like driver race, not an Important-class kernel vulnerability. The theoretical impact is incorrect hardware register access, which may affect GPIO integrity or availability. Realistic exploitation evidence points to misconfiguration or local device disruption, not kernel memory corruption, information disclosure, or privilege escalation.

## 5. One-sentence report phrase

A locking race in pca953x_irq_bus_sync_unlock() may allow concurrent GPIO or IRQ configuration to access regmap without i2c_lock, causing incorrect GPIO expander register reads or writes and possible local hardware or interrupt malfunction.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This can be auto-closed for urgent security triage because the patch supports a local hardware state race only, with no demonstrated memory corruption, privilege escalation, sensitive data exposure, or remote attack path.

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

Patch: gpio: pca953x: fix pca953x_irq_bus_sync_unlock regmap lock [ Upstream
Commit: e6a2f5f845f50b0c4299bace5111f56d3390a090
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e6a2f5f845f50b0c4299bace5111f56d3390a090

Changed files:
  drivers/gpio/gpio-pca953x.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=e6a2f5f845f50b0c4299bace5111f56d3390a090

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

The original Linux kernel CVE announcement for CVE-2026-74733 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74733

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: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: 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).