[CVE-2026-90242][LOW] iommu/vt-d: Fix iopf_refcount leak on RID domain replacement [ Upstream

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

CVE: CVE-2026-90242
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: iommu/vt-d: Fix iopf_refcount leak on RID domain replacement [ Upstream
Commit: 143cd37ce76527ddd6f6dbac4a89bde31fb8b0dc
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=143cd37ce76527ddd6f6dbac4a89bde31fb8b0dc
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90242
Analysis date: Fri, 18 Sep 2026 01:09:02 -0400
ActionableScore: 2
ActionableScore lower bound: 1
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-2026-90242 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90242

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-2026-90242	LOW	https://www.kernelcve.org/list/?q=CVE-2026-90242 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-772;*CWE-664;**CWE-400;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'An IOPF reference count leak in the Intel VT-d IOMMU RID domain attach path can occur when a device is moved from an old domain to a new domain. The new domain enables IOPF but the old domain reference is not always released, so info iopf_refcount may never return to zero. This can prevent iopf_queue_remove_device from running and can later trigger a WARN when iommu_disable_pci_pri is called during device release. For the CVSS the PR:L is used in the paranoid score because some deployments may delegate device assignment or IOMMU domain lifecycle operations to a less privileged service account or container root rather than full host root. The issue is not network reachable and requires local control over device or IOMMU management paths. Impact is mainly denial of service or device management disruption, with no concrete evidence of information disclosure or privilege escalation from the patch context.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)	YES	LOCK LEAK HARDWARE MEMORY  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	YES	NO	checked

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

ActionableScore=2
ActionableScoreLower=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 2
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate**::

No floor or cap was applied.

2. Signal breakdown

Conservative signals:

* +1 Concrete persistent kernel resource/reference leak. The patch establishes that RID domain replacement can leave info->iopf_refcount elevated because IOPF is enabled for the new domain without releasing the old domain reference.
* +0 WARN_ON only. The commit mentions iommu_disable_pci_pri() triggering WARN_ON(info->iopf_refcount), but does not establish a default fatal crash.
* +0 No UAF. The bug is a missing reference release, not post-free use.
* +0 No concrete C/I primitive. No disclosure, unauthorized modification, arbitrary write, stale object reuse, or privilege escalation path is shown.
* +0 No remote reachability. The path is IOMMU/device-domain management, not packet or network input.

Paranoid additional signal:

* +1 Limited availability or device-management disruption. The leaked IOPF reference prevents iopf_queue_remove_device() from running and may leave PRI/IOPF device state inconsistent at release time. This supports a low-end operational disruption interpretation, but not Important-class impact.

Non-awarded signals:

* Strong LPE leverage not awarded because there is no controlled reclaim, directed corruption, arbitrary write, callback control, or refcount takeover.
* Reliable kernel crash not awarded because WARN_ON alone is not enough without evidence of fatal behavior in default conditions.
* Resource exhaustion beyond the concrete reference leak not awarded because there is no evidence of broad host-wide accumulation from ordinary attacker activity.
* Concrete repeated release/refcount mutation not awarded. This is a missing release leak, not a first release followed by a second lifetime mutation through the same dangling reference.
* Active-state retirement signal not awarded as an Important-strength signal. The IOPF queue removal is skipped due to the leaked count, but the patch does not establish stale active translation use, stale DMA access, or secondary-index traversal causing corruption.

3. Reachability analysis

The affected operations are Intel VT-d IOMMU RID domain attach and identity-domain attach paths. Practical triggering requires control over device or IOMMU domain lifecycle, such as VFIO, iommufd, device assignment, driver attach, detach, or release flows.

Host-admin-equivalent privilege is plausible in many deployments, but the supplied evidence does not positively prove that host admin is always required for the complete trigger. A delegated device-management service account or preassigned VFIO device could potentially exercise relevant lifecycle paths. Therefore HostAdminRequired is UNKNOWN rather than YES.

Namespace-scoped privilege is NO from the supplied evidence. The bug is not tied to a network namespace or attacker-created namespace capability. No complete namespace-scoped trigger chain is established.

There is no direct network vector. There is no ordinary local unprivileged trigger shown. The required hardware/subsystem is Intel VT-d with IOPF/PRI-capable paths, but hardware specificity alone is not scored as a rare-hardware penalty.

No timing race is required. This appears to be an ordered reference-management bug during domain replacement.

4. Primitive and severity interpretation

The exact primitive is a persistent IOPF reference-count leak on RID domain replacement. The old domain reference is not released when a new domain is attached, and identity-domain attach similarly failed to release the old domain IOPF reference.

This is not a RealUAF. It is not a double release. It is not an arbitrary or directed write. It is not a security-boundary bypass. The demonstrated consequence is stale/inconsistent IOPF lifecycle accounting, skipped iopf_queue_remove_device(), and WARN_ON during device release.

PrimitiveClass is CLASS_C because the demonstrated behavior is invalid resource/lifetime state with possible device-management disruption, not a concrete exploitable corruption primitive.

ImportantCandidate is NO because the patch does not establish memory corruption, UAF, repeated lifetime mutation through a dangling reference, COW/ownership violation, authorization bypass, or a plausible privilege-escalation path.

AutoDowngradeAllowed is YES because the issue is a low-end resource/reference leak with no unresolved Important-grade primitive. It can be handled as ordinary Moderate/Low-like unless product-specific evidence shows that delegated users can repeatedly cause host-wide failure.

Likely operational severity is low to ordinary Moderate.

5. One-sentence report phrase

An Intel VT-d IOMMU RID domain replacement bug can leak an IOPF reference for the old domain, leaving PRI/IOPF cleanup incomplete and causing WARN_ON during device release, with impact limited to local device-management disruption unless stronger product-specific reachability is shown.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

The patch shows a concrete reference leak and cleanup inconsistency, but no UAF, no corruption primitive, no remote path, no authorization bypass, and no demonstrated privilege escalation.

7. Call-site confidence

Call-site confidence: medium

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

Patch: iommu/vt-d: Fix iopf_refcount leak on RID domain replacement [ Upstream
Commit: 143cd37ce76527ddd6f6dbac4a89bde31fb8b0dc
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=143cd37ce76527ddd6f6dbac4a89bde31fb8b0dc

Changed files:
  drivers/iommu/intel/iommu.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=143cd37ce76527ddd6f6dbac4a89bde31fb8b0dc

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

The original Linux kernel CVE announcement for CVE-2026-90242 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90242

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:L
  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: 1
  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).