[CVE-2026-80894][MODERATE 7.0] iommufd: Fix wrong hwpt passed to iommufd_auto_response_faults on replace [ Upstream

[CVE-2026-80894][MODERATE 7.0] iommufd: Fix wrong hwpt passed to iommufd_auto_response_faults on replace [ Upstream

[AL-KERNEL]

CVE: CVE-2026-80894
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: iommufd: Fix wrong hwpt passed to iommufd_auto_response_faults on replace [ Upstream
Commit: adb87155b67f9759ff010c0a99559f5bffa45dcf
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=adb87155b67f9759ff010c0a99559f5bffa45dcf
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80894
Analysis date: Fri, 04 Sep 2026 17:32:12 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
IOMMUFD device replacement passed the new hwpt together with an old domain handle to fault auto-response handling, potentially leaving old fault groups unresolved after old_handle is freed and creating a local DoS with a plausible stale-handle UAF concern.

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

The original Linux kernel CVE announcement for CVE-2026-80894 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80894

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
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CVE-2026-80894	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-80894 CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-825;*CWE-664;CWE-703;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'IOMMUFD device replacement can pass the new hwpt to iommufd_auto_response_faults together with old_handle from the old domain. Fault groups delivered before the replace are stored under the old hwpt fault state, so scanning the new hwpt can leave old fault groups unresolved while old_handle is later freed. This can cause at least a local denial of service in fault handling for an assigned device. In the worst still defensible interpretation, stale fault groups may retain or later compare a freed handle, making this a UAF candidate with possible confidentiality or integrity impact. For the CVSS the PR:L is used because reliable triggering requires local access to IOMMUFD device assignment or a delegated device control context, but not necessarily full host root. The issue is not network reachable and depends on fault capable IOMMUFD usage and device replace operations.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	WARNONLY HARDWARE  INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP	YES	NO	checked

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

ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Local delegated trigger: +1. Triggering requires local access to IOMMUFD device assignment or a process controlling an assigned device, not network access.
* Memory corruption, weak/indirect corruption candidate: +1. The wrong hwpt is used with old_handle, so pending fault groups may remain associated with the old fault state while the handle is freed.
* Real lifetime corruption: +1. The sequence can leave old fault state unresolved before kfree(old_handle), making stale handle lifetime a plausible concern.
* Privileged kernel/device-management lifetime path: +1. The bug is in IOMMUFD device replacement and fault handling, a trusted device-management path.
* Availability impact realistic: +1. At minimum, unresolved faults can break or stall fault handling for the assigned device.
* Rare/difficult-to-reach configuration: -1. The issue depends on fault-capable IOMMUFD usage, pending faults, and device replace operations.

Paranoid additional signal:

* Weak LPE concern: +1. A stale handle in fault delivery or response structures is a UAF candidate, but no controlled reclaim, overwrite, callback control, or concrete privilege-escalation primitive is shown.

## 3. Reachability analysis

The issue is local, not network reachable. A realistic trigger requires access to IOMMUFD and a fault-capable assigned device path, likely from a VMM, device-assignment manager, or delegated device-control context. This should not be treated as full PR:H in all deployments because VM or device-management processes may run with reduced privileges after setup. Namespaces and containers could matter only if device assignment or IOMMUFD access is explicitly delegated. The path is not a broad default user API and requires specific IOMMUFD fault handling and replace behavior.

## 4. Severity interpretation

This is stronger than an ordinary Moderate correctness bug because the one-line fix corrects an object/lifetime mismatch involving fault lists and a soon-freed handle. Realistic demonstrated impact is local DoS or broken device fault handling. The paranoid interpretation is actionable because stale fault groups may retain or later compare a freed handle, making this a UAF candidate. However, the patch does not demonstrate attacker-controlled reclaim, arbitrary write, callback dispatch, or a reliable LPE chain, so this is not a clear Important-class vulnerability from the patch alone.

## 5. One-sentence report phrase

IOMMUFD device replacement passed the new hwpt together with an old domain handle to fault auto-response handling, potentially leaving old fault groups unresolved after old_handle is freed and creating a local DoS with a plausible stale-handle UAF concern.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Manual review is required because this is a lifetime-sensitive IOMMUFD fault-handling bug involving a freed handle and possibly persistent fault groups. It should be checked for stale pointer traversal, later response matching, reference ownership, and whether a delegated VM or device-control process can trigger it without full host-root privileges.

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

Patch: iommufd: Fix wrong hwpt passed to iommufd_auto_response_faults on replace [ Upstream
Commit: adb87155b67f9759ff010c0a99559f5bffa45dcf
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=adb87155b67f9759ff010c0a99559f5bffa45dcf

Changed files:
  drivers/iommu/iommufd/device.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=adb87155b67f9759ff010c0a99559f5bffa45dcf

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

The original Linux kernel CVE announcement for CVE-2026-80894 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80894

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:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7

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: 4
  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).