* [CVE-2026-89451][MODERATE REGULAR] iommu/sva: Set handle->dev before the SVA handle is visible
@ 2026-09-11 22:37 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-11 22:37 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-89451
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: iommu/sva: Set handle->dev before the SVA handle is visible
Commit: bcffb1c75da8fc9d51168ff9f09d471c26507912
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bcffb1c75da8fc9d51168ff9f09d471c26507912
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89451
Analysis date: Fri, 11 Sep 2026 18:37:19 -0400
ActionableScore: 3
ActionableScore lower bound: unknown
Actionable bucket: Borderline / manual review recommended
Manual review required: YES
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-89451 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89451
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 REGULAR
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-2026-89451 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-89451 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:N/I:N/A:H';CWE-362;**CWE-476;CWE-665;BEST CVSS score: '4.7';DESCR 'An initialization race in iommu_sva_bind_device can expose a new SVA handle before handle dev is set. A concurrent bind can reuse that partially initialized handle and a later iommu_sva_unbind_device can dereference handle dev iommu_group while handle dev is NULL, causing a kernel crash. For the CVSS the PR:L is used because triggering requires local access to an SVA capable device or driver interface, but not necessarily full administrative privileges in deployments that delegate accelerator or PASID capable devices to users. The issue is not network reachable and depends on a race window between concurrent bind and unbind operations. Impact is denial of service via NULL pointer dereference. Confidentiality and integrity impact are not increased because the observed primitive is a NULL dereference rather than UAF, OOB access, or arbitrary write.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) YES LOCK SIMPLEFIX HARDWARE INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 YES NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=3
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 3
* Conservative score: 3
* Raw paranoid score: 3
* Paranoid score: 3
* Final recommended bucket: **Borderline / manual review recommended**::
No floor or cap changed the score.
2. Signal breakdown
Positive signals:
* +1 weak invalid structured state. The SVA handle is made visible in the PASID lookup before handle->dev is initialized, so a racing caller can observe a partially initialized kernel object.
* +1 reliable kernel crash / strong DoS. The commit directly states that iommu_sva_unbind_device() can dereference handle->dev->iommu_group while handle->dev is NULL.
* +1 security-sensitive IOMMU/SVA active object publication path. The bug is in device PASID/SVA binding state, so the invalid state occurs in a sensitive kernel device-address-space management path and deserves manual triage even though the demonstrated primitive is only NULL dereference.
Negative signals:
* No host-admin penalty applied. Host-admin-equivalent privilege is not positively established by the supplied evidence.
* No race penalty applied. Although this is a race, the evidence does not prove a one-shot externally uncontrollable race. If the relevant bind/unbind interface is reachable, repeated attempts appear plausible.
Important non-awarded signals:
* RealUAF not awarded. The patch establishes a partially initialized handle and NULL pointer dereference, not post-free object use.
* Concrete repeated release/refcount not awarded. There is no first lifetime-ending put/release followed by a second lifetime mutation on the same dangling reference.
* Structured stale-object leverage not awarded. The stale/reused object mechanics are not established.
* Strong LPE or controlled corruption not awarded. No controlled reclaim, arbitrary write, directed write, callback influence, or credential/security-field overwrite is shown.
* C/I impact not awarded. The demonstrated primitive is NULL dereference leading to crash.
* Remote reachability not awarded. This is not network-triggerable from the supplied evidence.
* Extra availability not awarded. The crash/DoS is already counted once.
3. Reachability analysis
The vulnerable path is local and tied to IOMMU SVA/PASID bind and unbind operations. A realistic trigger requires an SVA-capable device or driver path that can call iommu_sva_bind_device() concurrently and then unbind the returned handle.
Ordinary unprivileged reachability is not proven. Some deployments may delegate accelerator or PASID-capable device access to non-root users or service processes, but the supplied patch does not establish the complete userspace path or its exact permission model. Host-admin-equivalent privilege is also not proven, so HostAdminRequired is UNKNOWN rather than YES.
Namespace-scoped privilege is not established. The issue is not a netns or container-scoped capability path from the supplied evidence.
Prior setup may be required in practice: SVA/PASID-capable hardware, an enabled IOMMU/SVA configuration, and a device driver exposing SVA bind operations. These are material deployment prerequisites, but the supplied evidence does not prove rare or physical-only access. The race window is small, but likely repeatable if an attacker can drive concurrent bind/unbind operations.
4. Primitive and severity interpretation
The exact primitive is a partially initialized SVA handle becoming visible before handle->dev is assigned. A racing bind can reuse that handle, and a subsequent unbind can dereference handle->dev while it is NULL.
This is not a real UAF and not a concrete repeated-release/refcount bug. It is best classified as CLASS_C: invalid-state / NULL-dereference behavior with demonstrated kernel crash impact.
The demonstrated consequence is local denial of service via kernel crash. A stronger consequence such as privilege escalation is speculative because there is no evidence of memory reuse, stale post-lifetime access, arbitrary read/write, refcount takeover, or attacker-controlled structured replacement.
ImportantCandidate is NO because the established primitive is crash-only NULL dereference, not an unresolved Class B lifetime/corruption primitive. AutoDowngradeAllowed is YES because no meaningful exploitation leverage beyond DoS is established, though manual review is recommended due to the IOMMU/SVA context and unresolved privilege boundary.
5. One-sentence report phrase
An initialization race in iommu_sva_bind_device() can expose an SVA handle before handle->dev is initialized, allowing a concurrent bind and later unbind to trigger a NULL pointer dereference and local kernel crash.
6. Manual review recommendation
MANUAL CHECK RECOMMENDED
Reason: the demonstrated issue is DoS-only NULL dereference, but the exact userspace reachability and delegation model for SVA/PASID device access should be checked before automatic closure.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: iommu/sva: Set handle->dev before the SVA handle is visible
Commit: bcffb1c75da8fc9d51168ff9f09d471c26507912
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bcffb1c75da8fc9d51168ff9f09d471c26507912
Commit description:
iommu_attach_device_pasid() installs the new SVA attach handle in the
group PASID lookup before iommu_sva_bind_device() returns. A concurrent
bind can therefore find and reuse the same handle after iommu_sva_lock is
dropped.
handle->dev was initialized after dropping iommu_sva_lock. This leaves a
window where a racing bind can return a handle whose dev pointer is still
NULL. A subsequent iommu_sva_unbind_device() can then dereference it via
handle->dev->iommu_group.
Initialize handle->dev before releasing iommu_sva_lock so any visible SVA
handle is fully initialized.
Fixes: be51b1d ("iommu/sva: Refactoring iommu_sva_bind/unbind_device()")
Cc: [email protected]
Assisted-by: Qoder:Qwen-3.8-MAX-Preview
Signed-off-by: Shuai Xue <[email protected]>
Reviewed-by: Lu Baolu <[email protected]>
Reviewed-by: Kevin Tian <[email protected]>
Reviewed-by: Jason Gunthorpe <[email protected]>
Signed-off-by: Joerg Roedel <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
drivers/iommu/iommu-sva.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=bcffb1c75da8fc9d51168ff9f09d471c26507912
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-89451 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89451
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: Not available
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: unknown
Paranoid ActionableScore: 3
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 REGULAR
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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