[CVE-2026-53116][MODERATE 7.0] s390/ap: use generic driver_override infrastructure [ Upstream

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

CVE: CVE-2026-53116
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: s390/ap: use generic driver_override infrastructure [ Upstream
Commit: 8f2eca0570438b94602da1297353eb7b10dcb6cb
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8f2eca0570438b94602da1297353eb7b10dcb6cb
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53116
Analysis date: Thu, 25 Jun 2026 08:57:25 -0400
ActionableScore: 5
ActionableScore lower bound: 2
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A race in s390 AP `driver_override` handling can let AP binding revision read a freed override string during concurrent sysfs updates, creating a potential UAF with local DoS impact and limited worst-case confidentiality or integrity concern.

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

The original Linux kernel CVE announcement for CVE-2026-53116 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53116

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-2026-53116	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:L/A:H';BEST CVSS score: '5.8';DESCR 'A race in the s390 AP bus driver_override handling can make __ap_revise_reserved read driver_override while a concurrent driver_override_store frees or replaces the old string. This creates a potential use after free read during AP mask updates and device binding revision, with possible kernel crash or incorrect reprobe decisions. For the CVSS the PR:L is used for the paranoid score because reliable triggering requires local ability to write AP sysfs control attributes, but such access may be delegated to a service account or reduced capability administrator rather than full host administration. The issue is not network reachable and requires local control plane actions on an s390 system with AP devices. Impact is at least local denial of service via kernel crash and in worst case may allow limited confidentiality or integrity impact due to the UAF read primitive and should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4) 	MAYBE	UAF HARDWARE LINUS TEST 	-	-	checked

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

ActionableScore=5
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Generic memory corruption: +2. The commit explicitly describes a potential UAF on `driver_override`.
* Real lifetime corruption: +1. The old override string may be freed by `driver_override_store()` while another path reads it.
* Reliable kernel crash / strong DoS: +1. A stale string pointer used by `strcmp()` can plausibly crash the kernel.
* Privileged kernel/device-management memory corruption path: +1. The bug is in AP bus device binding and reprobe logic.
* Hard or unreliable race / special timing required: -1. Triggering requires racing AP mask updates with `driver_override_store()`.
* Requires admin/root/CAP-like access in typical deployments: -2. AP mask and driver override sysfs control is normally administrative.
* Rare AND difficult-to-reach subsystem/configuration: -1. This is s390 AP crypto hardware specific.

Paranoid additions/adjustments:

* Weak LPE concern: +1. The primitive is not a demonstrated arbitrary write, but UAF in driver binding logic can affect object selection and reprobe behavior.
* Confidentiality impact plausible: +1. UAF read of a freed string could theoretically expose limited stale kernel memory behavior, though no direct disclosure path is shown.
* Integrity impact plausible: +1. Incorrect driver match or reprobe decisions may affect device binding state.
* Reduced privilege interpretation instead of full admin penalty: use -1 instead of -2. In some deployments AP device control may be delegated to a service account, container root, or reduced capability administrator.

## 3. Reachability analysis

The bug is locally reachable through AP sysfs control paths on s390 systems with AP queue devices. A typical trigger requires the ability to update AP masks via `apmask_store()` or `aqmask_store()` and concurrently modify `driver_override`. In normal deployments this is administrator controlled, but delegated device-management setups can reduce the practical privilege requirement. It is not network reachable. The subsystem is hardware and architecture specific, so exposure is limited, but the affected path is a real device-management path rather than a purely theoretical debug path.

## 4. Severity interpretation

This is more than an ordinary Moderate cleanup because the patch fixes an explicit race leading to a potential UAF. Realistic exploitation is most likely a local crash or incorrect AP device reprobe/binding behavior. Strong privilege escalation is not demonstrated because the UAF appears to be a stale string read and comparison, not an attacker-controlled overwrite or reclaim primitive. Paranoid handling is still justified because lifetime bugs in driver binding paths can be underestimated and should not be auto-closed without manual review.

## 5. One-sentence report phrase

A race in s390 AP `driver_override` handling can let AP binding revision read a freed override string during concurrent sysfs updates, creating a potential UAF with local DoS impact and limited worst-case confidentiality or integrity concern.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: explicit UAF plus race in device binding logic. The likely practical impact is DoS, but the lifetime corruption and possible reduced-privilege delegated management model make this unsuitable for automatic closure.

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

Patch: s390/ap: use generic driver_override infrastructure [ Upstream
Commit: 8f2eca0570438b94602da1297353eb7b10dcb6cb
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8f2eca0570438b94602da1297353eb7b10dcb6cb

Changed files:
  drivers/s390/crypto/ap_bus.c
  drivers/s390/crypto/ap_bus.h
  drivers/s390/crypto/ap_queue.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=8f2eca0570438b94602da1297353eb7b10dcb6cb

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

The original Linux kernel CVE announcement for CVE-2026-53116 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53116

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: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).