* [CVE-2026-89453][LOW] iommu/amd: Put PCI device after handling PPR faults
@ 2026-09-11 21:22 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-11 21:22 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-89453
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: iommu/amd: Put PCI device after handling PPR faults
Commit: 1de4443f85e4405af00153cdf8ba73ff12a65036
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1de4443f85e4405af00153cdf8ba73ff12a65036
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89453
Analysis date: Fri, 11 Sep 2026 17:22:22 -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-2026-89453 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89453
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-2026-89453 LOW https://www.kernelcve.org/list/?q=CVE-2026-89453 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-772;*CWE-401;**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 'AMD IOMMU PPR fault handling can leak a PCI device reference because iommu_call_iopf_notifier obtains the requester with pci_get_domain_bus_and_slot but did not drop that reference after reporting or aborting the fault. A local actor with access to a workload or device path that can generate repeated PPR or IOPF faults may accumulate leaked references and interfere with device teardown, hot unplug, or resource cleanup. For the CVSS the PR:L is used because reliable triggering normally requires local access to a process, guest, or assigned device context that can cause IOMMU page faults, but it does not necessarily require full host administrator privileges. The issue is not network reachable by itself. Impact is denial of service through resource leakage and stuck device lifecycle operations. No confidentiality or integrity impact is assigned because the patch shows a missing reference release rather than a UAF, OOB access, or arbitrary write primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) YES SIMPLEFIX LEAK HARDWARE 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. No floor or cap applied.
* Raw paranoid score: 2
* Paranoid score: 2. No floor or cap applied.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
Positive signals:
* +1 Concrete persistent kernel resource/reference leak. `pci_get_domain_bus_and_slot()` returns a `pci_dev` with an elevated reference count, and the old code failed to call `pci_dev_put()` after both successful PPR fault reporting and the abort path.
* +1 paranoid only for accumulated availability impact. Repeated PPR/IOPF handling can accumulate leaked PCI device references and may interfere with device teardown, hot unplug, unbind, or cleanup.
Negative signals:
* No host-admin penalty applied. Host-admin-equivalent privilege is not positively established by the supplied evidence.
* No rare-hardware penalty applied. AMD IOMMU/PPR is hardware-dependent, but the input does not establish a physical-only or genuinely rare prerequisite.
* No race/timing penalty applied. This is an ordered missing-put reference leak, not a timing race.
Important non-awarded signals:
* RealUAF not awarded. This is a missing `pci_dev_put()` reference leak, not use-after-free.
* Concrete repeated release/refcount mutation not awarded. The bug leaks a reference; it does not perform a second put on a potentially dangling reference.
* Strong DoS/kernel crash not awarded. The patch supports reference leakage and possible lifecycle interference, not an immediate host-wide crash.
* C/I impact not awarded. No disclosure, unauthorized write, UAF, OOB access, or arbitrary write primitive is established.
* Remote reachability not awarded. The vulnerable operation is driven through IOMMU PPR/IOPF handling, not direct network input.
* Strong or weak LPE leverage not awarded. The patch does not establish controlled reclaim, refcount takeover, object replacement, or security-boundary bypass.
3. Reachability analysis
The reachable actor is unresolved. The fault path is entered when AMD IOMMU PPR/IOPF events are generated by a requester device. A local workload, guest, assigned device context, or userspace path with access to an IOMMU-fault-capable device may be able to generate repeated faults, but the supplied patch does not prove that an ordinary unprivileged local user can complete the trigger chain.
HostAdminRequired is therefore UNKNOWN rather than YES or NO. There is no evidence that a network namespace or attacker-created namespace supplies the complete required capability chain, so NamespaceScopedPrivilege is NO for this assessment. Prior host setup may exist in practice because IOMMU fault delivery depends on hardware, device configuration, and enabled PPR/IOPF paths. No direct network trigger is established.
4. Primitive and severity interpretation
The exact primitive is a persistent PCI device reference leak. `iommu_call_iopf_notifier()` obtains a `pci_dev` reference and previously failed to release it after handling the PPR entry. This can prevent normal reference-counted PCI device lifecycle cleanup.
This is not active structured UAF and not fixed stale storage. It is a resource/lifetime ownership leak. There is no first lifetime operation that may free the object followed by a second lifetime mutation through the same dangling reference. Therefore the repeated-release exception does not apply.
PrimitiveClass is CLASS_C because the demonstrated behavior is resource leakage and potential DoS/lifecycle interference without an independently useful corruption primitive. ImportantCandidate is NO because no memory corruption, authorization bypass, controlled object corruption, or unresolved lifetime mutation through a dangling reference is established. AutoDowngradeAllowed is YES because this is a concrete but low-end resource/reference leak with no evidence of LPE, C/I impact, network reachability, or strong kernel corruption.
Likely operational severity is Low to ordinary Moderate, mainly relevant for systems using AMD IOMMU PPR/IOPF with devices that can generate many page-fault requests.
5. One-sentence report phrase
AMD IOMMU PPR fault handling leaks PCI device references after each handled IOPF request, which may accumulate and interfere with device teardown or cleanup, but no UAF, memory corruption, privilege escalation, or direct network trigger is established.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
Reason: this is a concrete reference leak with possible availability impact, but the patch does not establish memory corruption, UAF, authorization bypass, network exposure, or privilege-escalation leverage.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: iommu/amd: Put PCI device after handling PPR faults
Commit: 1de4443f85e4405af00153cdf8ba73ff12a65036
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1de4443f85e4405af00153cdf8ba73ff12a65036
Commit description:
iommu_call_iopf_notifier() looks up the requester with
pci_get_domain_bus_and_slot(), which returns a PCI device with its
reference count incremented.
Neither the successful iommu_report_device_fault() path nor the abort
path drops that reference, so every handled PPR request leaks a PCI
device reference.
This is the same ownership rule that was fixed for the old iommu_v2
ppr_notifier() path by commit 6cf0981 ("iommu/amd: Fix pci device
refcount leak in ppr_notifier()"), but iommu_call_iopf_notifier() was
added later as a separate PPR/IOPF notifier path.
Drop the PCI device reference after handling the PPR entry.
Fixes: 978d626 ("iommu/amd: Add IO page fault notifier handler")
Cc: [email protected]
Assisted-by: Qoder:Qwen-3.8-MAX-Preview
Signed-off-by: Shuai Xue <[email protected]>
Reviewed-by: Vasant Hegde <[email protected]>
Signed-off-by: Joerg Roedel <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
drivers/iommu/amd/ppr.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=1de4443f85e4405af00153cdf8ba73ff12a65036
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-89453 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89453
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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