[CVE-2026-89795][LOW] PCI: Allow per function PCI slots to fix slot reset on s390 [ Upstream

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

CVE: CVE-2026-89795
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: PCI: Allow per function PCI slots to fix slot reset on s390 [ Upstream
Commit: 2050d900f9adbd6d6f38d30e182bcd9ad3108467
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2050d900f9adbd6d6f38d30e182bcd9ad3108467
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89795
Analysis date: Wed, 16 Sep 2026 14:49:45 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-89795 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89795

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-2026-89795	LOW	https://www.kernelcve.org/list/?q=CVE-2026-89795 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:H';CWE-706;CWE-404;*CWE-401;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'A PCI slot mapping bug on s390 can make a hotplug slot reset affect the wrong PCI function when multifunction PCI devices are represented in a shared PCI domain. This can disrupt an unintended device function and cause denial of service for networking, storage, or another assigned PCI function depending on the system configuration. The issue also includes a pci_slot reference cleanup problem that can leak memory during slot release. For the CVSS the PR:L is used for the paranoid score because delegated device management, service accounts, or reduced admin roles may have access to hotplug reset operations without full host control. The issue is not network reachable and requires local control of PCI hotplug or reset paths. Impact is availability loss only, with no evidence of memory corruption, information disclosure, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)	YES	LEAK HARDWARE LINUS  INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	NO	NO	checked

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

ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=YES
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 1
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate**::

No floor or cap changed the score.

2. Signal breakdown

Positive signals:

* +1: Unsafe PCI slot to function association. The bug can cause a hotplug slot reset to target the wrong PCI function on s390 multifunction PCI topology.
* +1: Availability impact. Resetting the wrong PCI function can disrupt an unintended device function such as networking or storage.
* +1: Concrete persistent kernel resource leak. The commit explicitly states that a pci_slot object is created for the function but is not correctly freed in pci_slot_release.

Negative signals:

* -2: Host admin equivalent access is required. PCI hotplug slot reset and PCI device management paths are host administrative operations over host owned PCI devices.
* -1: Specialized s390 PCI hotplug topology. The issue depends on s390 PCI pass through semantics and multifunction devices grouped in a shared PCI domain.

Important non-awarded signals:

* RealUAF not awarded. No use after free or stale post lifetime object use is established.
* Controlled corruption not demonstrated.
* Arbitrary write not demonstrated.
* Confidentiality and integrity impact not awarded because the patch supports wrong device selection and resource leak, not data disclosure or unauthorized modification of protected data.
* Remote reachability not established.
* Extra availability not awarded because the same wrong function reset is already counted as the DoS signal.
* Concrete repeated release or refcount mutation not awarded. The issue is a leak and matching bug, not a second lifetime mutation through a dangling reference.
* Strong LPE or privilege escalation not awarded.

3. Reachability analysis

The realistic trigger is local host PCI hotplug or reset control on s390. The vulnerable operation is not packet processing and is not reachable over the network.

The complete trigger requires access to PCI hotplug reset paths for host owned PCI functions. That is normally host administrator equivalent and not namespace scoped. No evidence shows that an ordinary unprivileged user or attacker controlled namespace can perform the complete reset operation.

There is a platform prerequisite: s390 with PCI functions exposed through the machine level hypervisor and multifunction topology grouped in a shared PCI domain. This is a specialized environment but not evidence of memory corruption.

No race or special timing requirement is central to the issue. The bug is a deterministic slot matching and lifetime cleanup problem.

4. Primitive and severity interpretation

The exact primitive is incorrect association between pci_slot objects and PCI functions on s390 multifunction PCI devices. This can make reset_slot operate on the wrong function. There is also a concrete pci_slot memory leak during release.

This is not active structured UAF and not fixed stale storage UAF. It is primarily wrong resource selection plus resource leak.

PrimitiveClass is CLASS_C because the demonstrated behavior is operational DoS or invalid resource targeting without an independently useful corruption primitive.

Demonstrated consequence is unintended PCI function reset and memory leak. Speculative consequence could be service disruption if the wrong function backs storage, networking, or another critical device, but the supplied evidence does not support privilege escalation, information disclosure, arbitrary write, or security boundary bypass.

ImportantCandidate=NO because no Class A primitive and no meaningful unresolved Class B lifetime corruption primitive is established.

AutoDowngradeAllowed=YES because this is a host-admin-gated device management issue with wrong reset target and leak only. It does not contain UAF, controlled corruption, authorization bypass, network reachability, or concrete repeated lifetime mutation.

Likely operational severity is Low to ordinary Moderate, depending on whether the affected PCI function is operationally critical.

5. One-sentence report phrase

On s390, shared pci_slot assignment for multifunction PCI devices can make a hotplug reset affect the wrong PCI function and leak pci_slot memory, causing local host-admin-triggered availability impact without evidence of memory corruption or privilege escalation.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: the patch supports a host-admin-gated wrong device reset and memory leak only, with no UAF, no controlled corruption, no network path, and no authorization boundary bypass.

7. Call-site confidence

Call-site confidence: high

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

Patch: PCI: Allow per function PCI slots to fix slot reset on s390 [ Upstream
Commit: 2050d900f9adbd6d6f38d30e182bcd9ad3108467
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2050d900f9adbd6d6f38d30e182bcd9ad3108467

Changed files:
  drivers/pci/pci.c
  drivers/pci/slot.c
  include/linux/pci.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=2050d900f9adbd6d6f38d30e182bcd9ad3108467

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

The original Linux kernel CVE announcement for CVE-2026-89795 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89795

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: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: unknown
  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).