[CVE-2026-64171][LOW] i2c: tegra: fix pm_runtime leak on mutex_lock failure

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

CVE: CVE-2026-64171
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: i2c: tegra: fix pm_runtime leak on mutex_lock failure
Commit: 8f7ed203b39004c02479a9156089d87d1ac2c1d8
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8f7ed203b39004c02479a9156089d87d1ac2c1d8
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64171
Analysis date: Sun, 19 Jul 2026 15:14:31 -0400
ActionableScore: 1
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like auto-close candidate
Manual review required: NO

Summary:
A missing pm_runtime_put() on the Tegra I2C mutex-lock failure path can leak a runtime PM reference and prevent runtime suspend, causing limited local availability or power-management impact without memory corruption or privilege escalation.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-64171 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64171

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-2026-64171	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-772;CWE-404;CWE-459;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '3.3';DESCR 'The i2c tegra transfer path can leak a runtime PM reference when pm_runtime_get_sync() succeeds but tegra_i2c_mutex_lock() fails. The leaked reference can keep the I2C controller active and prevent runtime suspend, causing a power management and availability degradation rather than memory corruption. For the CVSS the PR:L is used for the paranoid score because a local process with access to an exposed I2C interface or a delegated device access path may be able to trigger transfers, but reliable triggering also depends on the mutex lock failure condition. The issue is not network reachable. Impact is limited denial of service for power management or device suspend behavior, with no supported path to information disclosure or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like auto-close candidate (with actual score 1)  SKIP CVE-2026-64171 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: 6077cfd716fbd4d1f2a3702e49ae8bf65c072685 YES  NO NO unknown 	MAYBE	USB SIMPLEFIX LEAK HARDWARE LINUS 	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=1
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate / Low-like auto-close candidate**::

## 2. Signal breakdown

* Availability impact realistic: +1. A leaked runtime PM reference can keep the Tegra I2C controller active and prevent runtime suspend.
* Local unprivileged trigger: +1 only in the paranoid interpretation. This requires a local process with access to an exposed I2C interface or delegated device access.
* Hard or unreliable condition: -1. The leak requires tegra_i2c_mutex_lock() to fail after pm_runtime_get_sync() succeeds.
* Rare hardware or platform-specific path: -1. This is specific to the Tegra I2C controller path.
* No memory corruption: +0. The patch fixes a missing pm_runtime_put(), not UAF, OOB, double free, refcount takeover, or object confusion.
* No privilege escalation plausible: +0. There is no supported path to LPE.
* No network reachability: +0. The issue is local/device-path only.
* Call-site confidence: high. The affected function and error path are visible in the provided diff.

## 3. Reachability analysis

The bug can be triggered only through the Tegra I2C transfer path, and only when the SW mutex lock operation fails after runtime PM has been acquired. In typical deployments, direct I2C access is restricted to privileged users or selected service accounts, though some embedded systems may expose I2C devices to non-root local processes. Namespaces do not materially improve reachability unless device nodes are explicitly delegated into a container. The path is not network reachable and depends on Tegra hardware plus a specific error condition.

## 4. Severity interpretation

This behaves like a Low-like or ordinary Moderate resource-management bug, not an Important-class vulnerability. The realistic impact is limited availability or power-management degradation for the affected controller. There is no evidence of memory corruption, sensitive-object access, privilege escalation, or cross-boundary bypass. The paranoid score only accounts for possible local access to an exposed I2C interface, but the impact remains limited.

## 5. One-sentence report phrase

A missing pm_runtime_put() on the Tegra I2C mutex-lock failure path can leak a runtime PM reference and prevent runtime suspend, causing limited local availability or power-management impact without memory corruption or privilege escalation.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This can be auto-closed for security triage unless the product exposes Tegra I2C access broadly to untrusted local users and treats persistent runtime-suspend failure as a high operational risk.

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UPSTREAM PATCH SUMMARY
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Patch: i2c: tegra: fix pm_runtime leak on mutex_lock failure
Commit: 8f7ed203b39004c02479a9156089d87d1ac2c1d8
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8f7ed203b39004c02479a9156089d87d1ac2c1d8

Commit description:

If tegra_i2c_mutex_lock() fails, the function returns without calling
pm_runtime_put(), leaking the runtime PM reference acquired by the
preceding pm_runtime_get_sync(). This prevents the device from ever
entering runtime suspend.

Add the missing pm_runtime_put() before returning on lock failure.

Fixes: 6077cfd ("i2c: tegra: Add support for SW mutex register")
Signed-off-by: Saurav Sachidanand <sauravsc@amazon.com>
Cc: <stable@vger.kernel.org> # v7.0+
Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Link: https://lore.kernel.org/r/20260507221145.62183-2-sauravsc@amazon.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/i2c/busses/i2c-tegra.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=8f7ed203b39004c02479a9156089d87d1ac2c1d8

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

The original Linux kernel CVE announcement for CVE-2026-64171 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64171

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:L/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: 1

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).