[CVE-2026-90244][MODERATE 7.0] iommu/dma: Restore locking around msi_page_list [ Upstream

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

CVE: CVE-2026-90244
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: iommu/dma: Restore locking around msi_page_list [ Upstream
Commit: e3c53e9173a47d5ce1fae020f2c6b1fb3c1123c2
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e3c53e9173a47d5ce1fae020f2c6b1fb3c1123c2
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90244
Analysis date: Thu, 17 Sep 2026 19:21:26 -0400
ActionableScore: 6
ActionableScore lower bound: 5
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-90244 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90244

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-2026-90244	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-90244 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-362;CWE-667;*CWE-664;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A race in iommu_dma_get_msi_page can occur when VFIO type1 merges devices from different IOMMU groups into the same domain and those devices allocate software MSI pages in parallel. Different VFIO device fds can hold different group mutexes, so the existing group level locking does not serialize access to the shared msi_page_list. This can corrupt kernel list state and can lead at least to a local denial of service through a host kernel crash. For the CVSS the PR:L is used because reliable triggering requires local VFIO access or control of a VM with assigned devices, but does not necessarily require full host root privileges. The issue is not directly network reachable. For the paranoid score, the impact is treated as possible C:H/I:H/A:H because concurrent corruption of a shared kernel list is a plausible memory corruption primitive that deserves manual review.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 6)	YES	LOCK HARDWARE KPANIC MEMORY  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP	YES	NO	checked

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

ActionableScore=6
ActionableScoreLower=5
PrimitiveClass=CLASS_B
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO

1. ActionableScore

* Raw conservative score: 5
* Conservative score: 5. No floor or cap changed the score.
* Raw paranoid score: 6
* Paranoid score: 6. No floor or cap changed the score.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

Conservative signals:

* +2. Concrete active kernel list corruption. The patch states that two concurrent iommu_dma_get_msi_page() callers can corrupt the shared msi_page_list when VFIO type1 merges multiple groups into one domain.
* +1. Reliable host DoS concern. Corruption of an internal kernel list used in IOMMU DMA MSI setup can realistically lead to host kernel crash, list corruption failure, or broken interrupt setup.
* +1. Below-host-admin trigger in an already configured VM. The commit describes guest drivers probing and allocating MSIs in parallel, causing host-side VFIO_DEVICE_SET_IRQS on different device fds.
* +1. Security-sensitive virtualization and IOMMU context. The corrupted state belongs to host IOMMU/MSI handling for VFIO device assignment, so the failure crosses a guest to host management boundary rather than being only device-local metadata.

Paranoid additional signal:

* +1. Weak unresolved exploitation leverage. The corrupted shared list contains active structured MSI mapping state that may be traversed or reused later, so post-corruption behavior needs manual review. This is not scored as controlled corruption or arbitrary write.

Non-awarded signals:

* RealUAF not awarded. The patch establishes concurrent list corruption, not a concrete use-after-free or stale post-lifetime object use.
* Controlled reclaim not demonstrated.
* Arbitrary or directed kernel write not demonstrated.
* Confidentiality and integrity bonuses not awarded. The supplied evidence supports corruption and DoS, but not a concrete disclosure or unauthorized data modification primitive.
* Remote network reachability not awarded. The trigger is VFIO/IOMMU device assignment and MSI setup, not packet input.
* Hard race penalty not applied. The issue is a race, but the described parallel MSI allocation by two assigned devices is a repeatable concurrency scenario, not proven to be a narrow one-shot timing window.
* Host-admin penalty not applied to the trigger. Host setup is required to assign devices, but the described vulnerable operation can be driven by guest activity after the VM is configured.
* Strong LPE leverage +2 not awarded. There is no evidence of controlled object replacement, refcount takeover, callback influence, credential manipulation, or arbitrary host memory access.

3. Reachability analysis

The practical trigger requires a VM with at least two VFIO-assigned devices using the legacy VFIO type1 container where different IOMMU groups are merged into the same iommu_domain. It also requires an IOMMU that publishes IOMMU_RESV_SW_MSI, with ARM SMMU given as an example.

The attacker model is best treated as guest or VMM-mediated in an already provisioned VFIO assignment. A malicious guest can cause its drivers to probe devices and allocate MSIs in parallel, which leads to host-side VFIO_DEVICE_SET_IRQS calls on different device fds. The initial device assignment is prior privileged host setup, but the immediate trigger described by the commit does not require the attacker to be host administrator after that setup exists.

Namespace-scoped privilege is not relevant. This is not a network namespace or CAP_NET_ADMIN-in-netns case. It is also not directly network reachable.

Special hardware or configuration exists, but it is not enough to reduce the score below actionable range because VFIO passthrough and ARM SMMU-like deployments are realistic virtualization configurations, and the patch directly establishes host kernel list corruption.

4. Primitive and severity interpretation

The exact primitive is a race causing unsynchronized access to a shared msi_page_list in iommu_dma_get_msi_page(). The stale or inconsistent state is an active structured kernel list, not fixed stale storage.

This is not a concrete repeated release/refcount case. There is no first put/free followed by a second put/free on the same dangling reference. There is also no directly established UAF.

PrimitiveClass is CLASS_B because the patch establishes real kernel object/list corruption with unresolved exploitation leverage, but does not establish a CLASS_A primitive such as controlled reclaim, arbitrary write, callback control, or demonstrated privilege escalation.

The demonstrated consequence is at least host DoS or host instability through kernel list corruption in IOMMU/MSI handling. The speculative consequence is stronger memory corruption or privilege impact, but that is not proven by the supplied evidence and is therefore not scored as CLASS_A.

ImportantCandidate is YES because this is not a simple warning or device-local failure. It is host kernel list corruption in VFIO/IOMMU state reachable from a virtualization workflow. AutoDowngradeAllowed is NO because automatically closing it as ordinary Moderate would discard a concrete unresolved kernel corruption primitive.

5. One-sentence report phrase

A race in iommu_dma_get_msi_page() can allow parallel VFIO type1 MSI setup for devices sharing a merged IOMMU domain to corrupt the host msi_page_list, causing at least host DoS and requiring manual review for unresolved kernel corruption impact.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: concrete host kernel list corruption is established in VFIO/IOMMU MSI handling, and the exploitability beyond crash is unresolved even though controlled reclaim or arbitrary write is not demonstrated.

7. Call-site confidence

Call-site confidence: high

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

Patch: iommu/dma: Restore locking around msi_page_list [ Upstream
Commit: e3c53e9173a47d5ce1fae020f2c6b1fb3c1123c2
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e3c53e9173a47d5ce1fae020f2c6b1fb3c1123c2

Changed files:
  drivers/iommu/dma-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=e3c53e9173a47d5ce1fae020f2c6b1fb3c1123c2

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

The original Linux kernel CVE announcement for CVE-2026-90244 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90244

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:L/I:L/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: 5
  Paranoid ActionableScore: 6

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: YES
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).