[CVE-2026-53115][MODERATE 7.0] bus: fsl-mc: use generic driver_override infrastructure [ Upstream

[CVE-2026-53115][MODERATE 7.0] bus: fsl-mc: use generic driver_override infrastructure [ Upstream

[AL-KERNEL]

CVE: CVE-2026-53115
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: bus: fsl-mc: use generic driver_override infrastructure [ Upstream
Commit: 4911b836f35c034c36f102db4ecbe339b38e7d1d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4911b836f35c034c36f102db4ecbe339b38e7d1d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53115
Analysis date: Thu, 25 Jun 2026 05:28:30 -0400
ActionableScore: 5
ActionableScore lower bound: 2
Actionable bucket: Actionable Moderate at minimum / manual UAF review
Manual review required: YES

Summary:
A race in fsl-mc driver_override handling can let the bus match path read a freed override string during driver attach, creating a local UAF that is most likely to cause a kernel crash but deserves manual review due to kernel lifetime corruption.

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

The original Linux kernel CVE announcement for CVE-2026-53115 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53115

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 7.0
Manual review required: YES

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

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

CVE-2026-53115	MODERATE	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';*CWE-416;CWE-362;CWE-667;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'fsl-mc driver matching can read driver_override without the device lock while another path updates or frees the same string. This creates a race based use-after-free in the bus match path and can lead to a kernel crash or incorrect driver matching under a narrow timing window. For the CVSS the PR:L is used in the paranoid score because some deployments may delegate device binding or VFIO related device management to a reduced privilege user or service, even though normal host systems usually require administrator privileges. The issue is local and is not directly network reachable. Impact is at least denial of service via kernel crash. In the paranoid view, limited confidentiality or integrity impact is kept because a stale kernel pointer is read during driver matching, but the patch does not show an arbitrary write primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum / manual UAF review (with actual score 4) 	MAYBE	LOCK UAF HARDWARE LINUS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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

ActionableScore=5
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum / manual UAF review**::

## 2. Signal breakdown

Paranoid scoring:

* +2 Generic memory corruption: explicit use-after-free is described. `fsl_mc_bus_match()` can read `driver_override` while another path updates or frees it.
* +1 Real lifetime corruption: stale pointer after free / unlocked lifetime race on `driver_override`.
* +1 Reliable kernel crash / strong DoS: stale string use in `strcmp()` can plausibly cause kernel oops or panic.
* +1 Weak LPE concern: UAF occurs in kernel driver matching, but the primitive appears read-oriented and constrained. No arbitrary write or controlled reclaim primitive is shown.
* +1 Local lower-privilege or delegated trigger concern: normal systems require admin-level device management, but VFIO or device-management delegation can reduce the practical privilege boundary.
* +1 Privileged kernel/device-management memory corruption path: bug is in bus matching and VFIO-related device override handling.
* -1 Hard or unreliable race: requires timing between `__driver_attach()` match and override update/free.
* -1 Constrained primitive: stale pointer is used as a string for matching. No attacker-controlled overwrite target or payload is shown.

Conservative score keeps the UAF and DoS signals but applies the typical admin/device-management requirement, resulting in ActionableScoreLower=2.

## 3. Reachability analysis

This is local, not network reachable. Typical triggering requires access to fsl-mc device management paths such as driver binding, unbinding, device removal, or override updates. On normal host systems this is usually restricted to root or privileged management services.

Namespaces and containers matter only if device sysfs or VFIO management is delegated into a reduced-privilege environment. In that case PR can be closer to local lower-privilege rather than full host-root. The affected subsystem is hardware/platform specific, so exposure is not broad by default, but systems using NXP fsl-mc / DPAA2 and VFIO assignment should not auto-close it without review.

## 4. Severity interpretation

This behaves like an Actionable Moderate rather than a strong Important candidate. The patch supports a real UAF/lifetime race, so manual review is justified. Realistic impact is most likely kernel crash or incorrect driver matching under a narrow race window. Privilege escalation is only weakly plausible because the observed primitive is a stale string read during matching, not a demonstrated reclaim, arbitrary write, or controlled object-confusion primitive.

## 5. One-sentence report phrase

A race in fsl-mc driver_override handling can let the bus match path read a freed override string during driver attach, creating a local UAF that is most likely to cause a kernel crash but deserves manual review due to kernel lifetime corruption.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the patch explicitly fixes a UAF in a kernel device-management path, and although the primitive appears constrained and usually privileged, delegated VFIO or device-management setups may lower practical privileges.

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

Patch: bus: fsl-mc: use generic driver_override infrastructure [ Upstream
Commit: 4911b836f35c034c36f102db4ecbe339b38e7d1d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4911b836f35c034c36f102db4ecbe339b38e7d1d

Changed files:
  drivers/bus/fsl-mc/fsl-mc-bus.c
  drivers/vfio/fsl-mc/vfio_fsl_mc.c
  include/linux/fsl/mc.h

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=4911b836f35c034c36f102db4ecbe339b38e7d1d

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

The original Linux kernel CVE announcement for CVE-2026-53115 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53115

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:L/I:L/A:H
  The Best / paranoid CVSS score: 5.8

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: 2
  Paranoid ActionableScore: 5

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 7.0

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).