[CVE-2026-89446][LOW] iommufd: Release current IOAS on xa_store() failure

[CVE-2026-89446][LOW] iommufd: Release current IOAS on xa_store() failure

[AL-KERNEL]

CVE: CVE-2026-89446
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: iommufd: Release current IOAS on xa_store() failure
Commit: 4c33d00ad9a911e87ea222986f732ce072e3aa26
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4c33d00ad9a911e87ea222986f732ce072e3aa26
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89446
Analysis date: Sat, 12 Sep 2026 01:48:32 -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-2026-89446 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89446

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-2026-89446	LOW	https://www.kernelcve.org/list/?q=CVE-2026-89446 CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';*CWE-772;CWE-667;CWE-404;**CWE-400;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'iommufd_take_all_iova_rwsem() can leak the current IOAS write lock and object reference when xa_store() fails before the IOAS is inserted into the temporary xarray. The unwind helper only releases entries already present in that xarray, so the current IOAS can remain locked and referenced after the error path returns. For the CVSS the PR:L is used because a local process with access to iommufd or a related VFIO workflow is needed to reach this interface, but full host administrator privileges are not necessarily required in all deployments. The issue is not network reachable and requires a local control path plus an allocation failure or similar xa_store() error condition. Impact is denial of service through a leaked lock or resource reference, with no supported evidence of memory corruption, information disclosure, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)	YES	SIMPLEFIX  DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS_AND_CIANNH	YES	NO	checked

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

ActionableScore=2
ActionableScoreLower=1
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 1
* Conservative score: 1. No floor or cap changed the score.
* Raw paranoid score: 2
* Paranoid score: 2. No floor or cap changed the score.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

Conservative signals:

* +1 Concrete persistent kernel resource/reference leak. The function takes the current IOAS object reference and the `iova_rwsem` write lock before `xa_store()`. If `xa_store()` fails, that IOAS is not inserted into `ioas_list`, so the generic unwind helper cannot release it.
* +0 Reliable kernel crash not awarded. The patch supports a leaked lock/reference and possible blocked operations, not a demonstrated panic or Oops.
* +0 Confidentiality and integrity not awarded. There is no UAF, OOB access, arbitrary write, information disclosure, ownership violation, or authorization bypass.
* +0 Concrete repeated release/refcount not awarded. The bug is a missing release/refcount decrement, not a second lifetime mutation through a dangling reference.
* +0 Race/timing penalty not applied. This is an ordered error path, not a hard race.
* +0 Host-admin penalty not applied. Host-admin-equivalent privilege is not positively established from the supplied evidence.

Paranoid additional signal:

* +1 Availability impact realistic. A leaked write lock on an IOAS can plausibly block later operations in the affected iommufd/VFIO workflow, so a localized DoS interpretation is defensible.

Non-awarded material signals:

* Controlled reclaim not demonstrated.
* Arbitrary read/write not demonstrated.
* Real UAF not established.
* Concrete repeated lifetime/refcount mutation not established.
* Security boundary bypass not established.
* Remote reachability not established.
* Important-grade exploitation leverage not established.

Repeated-release/refcount checklist:

* First release can end lifetime: not applicable. The vulnerable path misses a release rather than performing an early release.
* Exact same reference survives as dangling: no. The extra reference keeps the object alive.
* Second operation mutates lifetime/refcount through freed storage: no.
* +1 Concrete repeated release/refcount awarded: no.
* Paranoid repeated-refcount leverage +1 awarded: no.
* FLOOR 5 applied: no.

3. Reachability analysis

The reachable actor is a local process using iommufd or a related VFIO/device-assignment workflow. The supplied context supports PR:L style local access in some deployments, but it does not fully prove that an ordinary unprivileged user can complete the full setup without prior device delegation or permissions. Therefore HostAdminRequired is UNKNOWN rather than YES or NO.

The issue is not network reachable. Namespace-scoped privilege is not established. The complete trigger chain is not shown to be performable inside attacker-created namespaces.

The practical trigger also requires `xa_store()` failure, likely from allocation failure or similar xarray insertion failure. This makes reliable triggering less straightforward, but it is not a race and does not establish a separate hard-timing penalty. Prior privileged setup may exist in real systems if a device or iommufd access must be delegated to a VMM or service account.

4. Primitive and severity interpretation

The exact primitive is a missing error-path cleanup of the current IOAS object reference and `iova_rwsem` write lock. This is a concrete resource/reference and lock leak.

This is not an active post-free stale-object use. The IOAS object is kept alive by the leaked reference, so the evidence points to resource retention and lock contention rather than UAF or memory corruption. There is no concrete second `put`, `release`, `free`, or refcount decrement through a potentially dangling reference.

PrimitiveClass is NONE because no meaningful corruption, lifetime-after-free, authorization, COW ownership, or boundary-bypass primitive is established. The demonstrated consequence is local denial of service or workflow disruption through a leaked lock/reference. Stronger consequences such as privilege escalation, information disclosure, arbitrary kernel write, or controlled object corruption are speculative and not supported by the patch.

ImportantCandidate is NO because this is a local error-path resource/lock leak without memory corruption or security-boundary impact. AutoDowngradeAllowed is YES because automatic closure as ordinary Moderate/Low-like is reasonable unless product-specific evidence shows untrusted tenants can reliably trigger persistent service-wide deadlock.

5. One-sentence report phrase

An iommufd error path can leak the current IOAS reference and write lock when xa_store() fails before insertion into the temporary xarray, causing a local resource or lock based DoS without evidence of memory corruption or privilege escalation.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: the patch establishes a missing cleanup on an allocation failure path, but no UAF, repeated refcount mutation, controlled corruption, authorization bypass, or network exposure is supported.

7. Call-site confidence

Call-site confidence: medium

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

Patch: iommufd: Release current IOAS on xa_store() failure
Commit: 4c33d00ad9a911e87ea222986f732ce072e3aa26
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4c33d00ad9a911e87ea222986f732ce072e3aa26

Commit description:

iommufd_take_all_iova_rwsem() takes an object reference and the
iova_rwsem write lock before storing the IOAS in the temporary ioas_list
xarray.

If xa_store() fails, the current IOAS has not been inserted into
ioas_list yet. iommufd_release_all_iova_rwsem() only unwinds IOAS
objects already present in that xarray, so it cannot release the current
IOAS.

Release the current IOAS rwsem and object reference before unwinding the
previously stored entries.

Fixes: 051ae5a ("iommufd: Lock all IOAS objects")
Cc: stable@vger.kernel.org
Assisted-by: Qoder:Qwen-3.8-MAX-Preview
Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/iommu/iommufd/ioas.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=4c33d00ad9a911e87ea222986f732ce072e3aa26

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

The original Linux kernel CVE announcement for CVE-2026-89446 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89446

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:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: 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).