[CVE-2026-63935][LOW] iio: adc: nxp-sar-adc: fix division by zero in write_raw

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

CVE: CVE-2026-63935
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: iio: adc: nxp-sar-adc: fix division by zero in write_raw
Commit: cb6ea15e7d3c7518f806975a06b7d4c0a26402ea
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cb6ea15e7d3c7518f806975a06b7d4c0a26402ea
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63935
Analysis date: Sun, 19 Jul 2026 17:10:44 -0400
ActionableScore: 2
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A local user or process with write access to the NXP SAR ADC IIO `sampling_frequency` sysfs attribute can write an invalid value and trigger a kernel division-by-zero crash, with no 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-2026-63935 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63935

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-2026-63935	LOW	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	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:H';CWE-369;CWE-191;*CWE-20;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'A local input validation flaw in the NXP SAR ADC IIO driver allows sampling_frequency to be used as a divisor before checking that it is positive. A user or local process with write access to the IIO sysfs attribute can write zero or a negative value and trigger a division-by-zero in nxp_sar_adc_write_raw(), which may crash the kernel. The same path can also underflow the unsigned inpsamp calculation when the computed cycle count is smaller than NXP_SAR_ADC_CONV_TIME, potentially programming an invalid large timing value. For the CVSS the PR:L is used for the paranoid case because some deployments may delegate write access to IIO sysfs attributes or run device control helpers under reduced privileges. The issue is not network reachable and the impact is denial of service only, with no supported path to memory corruption or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)  SKIP CVE-2026-63935 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: 4434072a893e4864519c167947083ff3e4cc2d95 YES  NO NO unknown 	MAYBE	OOB SIMPLEFIX IMPROVEONLY LINUS  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	-	-	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:

* Reliable kernel crash / strong DoS: +1. Writing zero to `sampling_frequency` can trigger division by zero in kernel context.
* Requires admin/root/CAP_* in typical deployments: -2. Writing IIO device sysfs control attributes is usually restricted to root or a privileged device-management service.
* Rare AND difficult-to-reach subsystem/configuration: -1. This is specific to the NXP SAR ADC driver on limited S32G2/3 style hardware.

Conservative total is clamped to 0.

Paranoid signals:

* Local unprivileged trigger: +1. Some deployments may delegate write access to IIO sysfs attributes or expose the device through less privileged control helpers.
* Reliable kernel crash / strong DoS: +1. The division by zero is a direct crash-class condition once the vulnerable write is allowed.
* Rare AND difficult-to-reach subsystem/configuration: -1. Hardware and driver exposure are not broad.
* Availability impact realistic: +1. If the sysfs write is reachable, the crash trigger is simple and deterministic.

Paranoid total: 2.

No memory corruption, UAF, OOB write, refcount issue, page-cache corruption, security-boundary bypass, or privilege-escalation primitive is supported by the patch.

## 3. Reachability analysis

The bug is triggered by writing an invalid value to the IIO `sampling_frequency` sysfs attribute for the affected NXP SAR ADC device. In normal deployments this is a local privileged device-management operation, usually requiring root or a service with delegated device permissions. It is not network reachable. Containers or namespaces do not normally make this reachable unless the host explicitly exposes the relevant sysfs device node with write permissions. Realistic exploitation requires affected hardware, the driver loaded, and write access to the attribute.

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like local DoS issue. The division by zero can crash the kernel, but the patch is a validation-only fix and does not show memory corruption or a path to privilege escalation. The unsigned underflow can program an invalid large timing value, but no downstream corruption primitive is demonstrated.

## 5. One-sentence report phrase

A local user or process with write access to the NXP SAR ADC IIO `sampling_frequency` sysfs attribute can write an invalid value and trigger a kernel division-by-zero crash, with no evidence of memory corruption or privilege escalation.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: this is a validation-only local DoS in a hardware-specific driver, with no demonstrated memory corruption, no network reachability, and no plausible LPE primitive in the provided patch context.

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

Patch: iio: adc: nxp-sar-adc: fix division by zero in write_raw
Commit: cb6ea15e7d3c7518f806975a06b7d4c0a26402ea
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cb6ea15e7d3c7518f806975a06b7d4c0a26402ea

Commit description:

Add a validation check for the sampling frequency value before using it
as a divisor. A user writing zero or a negative value to the
sampling_frequency sysfs attribute triggers a division by zero in the
kernel.

Also prevent unsigned integer underflow when the computed cycle count is
smaller than NXP_SAR_ADC_CONV_TIME, which would wrap the u32 inpsamp to
a huge value.

Fixes: 4434072 ("iio: adc: Add the NXP SAR ADC support for the s32g2/3 platforms")
Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/iio/adc/nxp-sar-adc.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=cb6ea15e7d3c7518f806975a06b7d4c0a26402ea

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

The original Linux kernel CVE announcement for CVE-2026-63935 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63935

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:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.5

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).