[CVE-2026-53280][LOW] iommu: Fix NULL group->domain dereference in pci_dev_reset_iommu_done()

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

CVE: CVE-2026-53280
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: iommu: Fix NULL group->domain dereference in pci_dev_reset_iommu_done()
Commit: 17194cd0dd236e732d116d50840d795ca50ef196
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=17194cd0dd236e732d116d50840d795ca50ef196
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53280
Analysis date: Fri, 26 Jun 2026 17:04:14 -0400
ActionableScore: 1
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A NULL group domain dereference in pci_dev_reset_iommu_done can crash the kernel when default IOMMU domain allocation fails during first probe and a later PCI reset completion attempts to re attach the device.

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

The original Linux kernel CVE announcement for CVE-2026-53280 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53280

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-53280	LOW	CHECK	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-476;CWE-754;CWE-703;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'pci_dev_reset_iommu_done can dereference a NULL IOMMU group domain when a default domain allocation fails during the first device probe and a later PCI reset completion tries to re attach the device. This leads to a NULL pointer dereference in __iommu_attach_device through domain ops attach_dev and can crash the kernel. For the CVSS the PR:L is used for the paranoid score because some deployments may delegate PCI reset or device management to a reduced capability root, container root, or service account, although typical systems require administrator privileges. The issue is not network reachable and requires local control over a PCI reset or probe related path. Impact is denial of service only because the patch supports a NULL dereference crash and does not show a UAF, OOB access, information leak, or privilege escalation primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)  SKIP CVE-2026-53280  SKIP The Fixes patch not applied yet, so unlikely that actual: c279e83953d937470f8a6e69b69f62608714f13f YES  NO NO unknown 	MAYBE	LOCK INIT WARNONLY SIMPLEFIX HARDWARE 	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=1
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate / Low-like**::

## 2. Signal breakdown

Conservative signals:

* Reliable kernel crash / strong DoS: +1. The patch fixes a NULL dereference of group->domain through domain->ops->attach_dev in __iommu_attach_device().
* Requires admin/root/CAP_* in typical deployments: -2. Triggering normally requires PCI reset/probe or device-management control.
* Rare AND difficult-to-reach condition: -1. The crash requires default domain allocation failure during first probe and a later reset completion path.
* Generic memory corruption: +0. This is a NULL pointer dereference, not UAF, OOB write, double free, or object lifetime corruption.
* Privilege escalation plausible: +0. No reclaim primitive, controlled overwrite, stale pointer use, or corruption sink is shown.
* Confidentiality/Integrity impact: +0. No information leak or write primitive is supported by the patch.

Paranoid interpretation:

* Score raised to 1 by treating delegated PCI/device-management control as a reduced-privilege operational model rather than full host-root equivalence.
* Still no memory corruption or LPE signal is justified.

## 3. Reachability analysis

The bug is locally reachable through PCI/IOMMU reset or probe-related paths after a failed default domain allocation. In normal deployments this is controlled by privileged kernel/device-management operations, not by an unprivileged local user. Containers or service accounts could matter only if PCI reset or device management is delegated, but that is not a default exposure. The issue is not network reachable and is not packet-triggered.

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like kernel DoS issue. The demonstrated primitive is a NULL pointer dereference leading to kernel crash. Theoretical impact beyond DoS is not supported because the patch does not indicate UAF, stale lifetime reuse, OOB access, arbitrary write, page-cache corruption, or sensitive-object access.

## 5. One-sentence report phrase

A NULL group domain dereference in pci_dev_reset_iommu_done can crash the kernel when default IOMMU domain allocation fails during first probe and a later PCI reset completion attempts to re attach the device.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: this is a local privileged or delegated-device-management NULL dereference DoS with no supported memory corruption, privilege escalation, network reachability, or security-boundary bypass primitive.

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

Patch: iommu: Fix NULL group->domain dereference in pci_dev_reset_iommu_done()
Commit: 17194cd0dd236e732d116d50840d795ca50ef196
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=17194cd0dd236e732d116d50840d795ca50ef196

Commit description:

Local sashiko review pointed it out that group->domain could be NULL when
a default domain fails to allocate during the first probe, which can crash
at domain->ops->attach_dev dereference in __iommu_attach_device() invoked
by pci_dev_reset_iommu_done().

pci_dev_reset_iommu_prepare() is fine as an old_domain pointer can be NULL.

Skip the re-attach in pci_dev_reset_iommu_done() to fix the bug.

Fixes: c279e83 ("iommu: Introduce pci_dev_reset_iommu_prepare/done()")
Cc: stable@vger.kernel.org
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/iommu/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=17194cd0dd236e732d116d50840d795ca50ef196

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

The original Linux kernel CVE announcement for CVE-2026-53280 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53280

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:H/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: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: 0
  Paranoid ActionableScore: 1

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).