[CVE-2026-43318][MODERATE REGULAR] drm/amdgpu: fix sync handling in amdgpu_dma_buf_move_notify [ Upstream

[CVE-2026-43318][MODERATE REGULAR] drm/amdgpu: fix sync handling in amdgpu_dma_buf_move_notify [ Upstream

[AL-KERNEL]

CVE: CVE-2026-43318
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: drm/amdgpu: fix sync handling in amdgpu_dma_buf_move_notify [ Upstream
Commit: 82a7ea35a1526bef8ae170c33ff80e5db7728961
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=82a7ea35a1526bef8ae170c33ff80e5db7728961
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-43318
Analysis date: Sat, 01 Aug 2026 12:37:55 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline Moderate. Manual review recommended
Manual review required: YES

Summary:
AMDGPU dma-buf move notification could update another process GPU VM page table while a shared BO is still in use, causing GPU page faults or reset, with limited paranoid concern for cross-process GPU memory effects but no demonstrated kernel memory corruption primitive.

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

The original Linux kernel CVE announcement for CVE-2026-43318 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-43318

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-2026-43318	MODERATE	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:L/I:L/A:H';CWE-662;CWE-362;CWE-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.8';DESCR 'AMDGPU dma buf move notification can update a VM page table while another process or GPU job is still using the shared BO. This can happen during BO migration or invalidation in multi GPU dma buf sharing scenarios, for example when one process exports a buffer from GPU0 and another process imports it on GPU1 while P2P access is not available. The likely result is a GPU page fault, GPU reset, display disruption, or denial of service rather than a direct kernel memory corruption primitive. For the CVSS the PR:L is used because a local user with access to DRM render or graphics interfaces may be able to create or use shared dma buf objects without full administrator privileges. The issue is not network reachable and requires local graphics or GPU access plus a specific synchronization window, so AC:H is appropriate. Impact is at least local denial of service and in the paranoid interpretation may allow limited confidentiality or integrity impact through incorrect GPU VM page table state, so it should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline Moderate. Manual review recommended (with actual score 4) 	MAYBE	HARDWARE MEMORY  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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

ActionableScore=4
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 4
* Final recommended bucket: **Borderline Moderate. Manual review recommended**

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. A local user with access to DRM render or graphics interfaces may be able to create or use shared dma-buf BOs without full administrator privileges.
* Reliable device/GPU DoS: +1. The commit describes a likely GPU page fault when the page table is updated while a GPU blit job is still running.
* Privileged device-management / MMU-state corruption concern: +1. The bug affects AMDGPU VM page table update synchronization for shared BO movement.
* Hard or timing-dependent synchronization window: -1. The problematic ordering depends on concurrent BO movement, command submission, and another user of the shared BO.
* Specific hardware/runtime configuration: -1. The example requires multi-GPU dma-buf sharing and a case where P2P PCI access is not supported.

Paranoid additional signal:

* Weak confidentiality/integrity concern through incorrect GPU VM state: +1. The patch prevents updating another process VM page table while the BO is still in use, so limited cross-process or wrong-object GPU memory effects are worth manual review, but there is no demonstrated kernel arbitrary write, UAF reclaim, or CPU-side memory corruption primitive.

## 3. Reachability analysis

The bug is locally reachable through AMDGPU dma-buf sharing and BO migration paths. A realistic trigger requires local graphics or render-node access, multiple users of a shared BO, and a synchronization window where one process moves or invalidates the BO while another GPU job is still using it.

Namespaces and containers may matter if DRM render nodes are passed into containers or service sandboxes. This should not be treated as PR:H in practical triage because access to render nodes is commonly delegated to non-root desktop, compositor, container, or GPU workload users.

The path is not network reachable. It is also not a generic default path for every AMDGPU system because the described scenario depends on shared dma-buf use and multi-GPU or cross-device access conditions.

## 4. Severity interpretation

This behaves more like a borderline to actionable Moderate GPU DoS issue than an Important-class kernel memory corruption issue. The realistic impact is GPU page fault, GPU reset, display disruption, or denial of service.

Theoretical confidentiality or integrity impact is not impossible because the bug involves GPU VM page table state for shared BOs across processes. However, the patch does not show attacker-controlled CPU memory corruption, UAF reclaim, arbitrary write, refcount takeover, or a demonstrated privilege escalation path. Therefore the conservative score stays moderate, while the paranoid score recommends manual review.

## 5. One-sentence report phrase

AMDGPU dma-buf move notification could update another process GPU VM page table while a shared BO is still in use, causing GPU page faults or reset, with limited paranoid concern for cross-process GPU memory effects but no demonstrated kernel memory corruption primitive.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Manual review is recommended because the bug touches GPU VM page table synchronization and shared BO ownership across processes. It should not be auto-closed as a simple DoS, but the available patch context does not justify Important-class treatment without additional evidence of memory disclosure, write primitive, or privilege escalation.

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

Patch: drm/amdgpu: fix sync handling in amdgpu_dma_buf_move_notify [ Upstream
Commit: 82a7ea35a1526bef8ae170c33ff80e5db7728961
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=82a7ea35a1526bef8ae170c33ff80e5db7728961

Changed files:
  drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.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=82a7ea35a1526bef8ae170c33ff80e5db7728961

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

The original Linux kernel CVE announcement for CVE-2026-43318 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-43318

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:L/I:L/A:H
  The Best / paranoid CVSS score: 5.8

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: 3
  Paranoid ActionableScore: 4

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 alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).