[CVE-2026-80618][MODERATE 7.0] drm/amdkfd: Avoid double-unpin of DOORBELL/MMIO BOs on free [ Upstream

[CVE-2026-80618][MODERATE 7.0] drm/amdkfd: Avoid double-unpin of DOORBELL/MMIO BOs on free [ Upstream

[AL-KERNEL]

CVE: CVE-2026-80618
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: drm/amdkfd: Avoid double-unpin of DOORBELL/MMIO BOs on free [ Upstream
Commit: 461ae406ae12107ebb321cabe561434c27aaea58
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=461ae406ae12107ebb321cabe561434c27aaea58
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80618
Analysis date: Fri, 28 Aug 2026 06:36:20 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A local AMDGPU KFD user may trigger a double unpin of DOORBELL or MMIO remap BOs, causing TTM pin count underflow and possible GPU driver instability, with weak but review worthy concern around mapped GPU memory lifetime state.

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

The original Linux kernel CVE announcement for CVE-2026-80618 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80618

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-2026-80618	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H';*CWE-672;CWE-667;*CWE-664;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '6.6';DESCR 'A double unpin condition in the AMD KFD GPUVM free path can occur because DOORBELL and MMIO remap BOs were unpinned before checking whether the BO was still mapped to GPU memory. If the free operation returns EBUSY, the BO remains alive but has already lost its pin state, and a later process teardown can unpin it again and trigger a TTM pin count underflow warning. For the CVSS the PR:L because a local user with access to KFD or AMDGPU render devices may be able to allocate and free such GPU memory objects without full administrator privileges. The issue is not network reachable and requires local GPU device access. Impact is at least local denial of service or driver instability. In the paranoid interpretation, limited confidentiality or integrity impact is possible because a mapped GPU visible BO may become unpinned while still alive, which can affect GPU memory management state and should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)  SKIP CVE-2026-80618 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	OOB UAF HARDWARE  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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

ActionableScore=5
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. A local user with access to AMDGPU or KFD render devices may be able to allocate and free the affected BO types without full host root.
* Real lifetime corruption: +1. The bug corrupts BO pinning lifetime state by unpinning an object that remains alive after the function returns EBUSY.
* Availability impact realistic: +1. The demonstrated result is a TTM pin count underflow warning and possible GPU driver instability during process teardown.

Paranoid additional signals:

* Weak or indirect corruption candidate: +1. The stale unpinned state affects a still mapped GPU visible BO, which is more serious than pure bookkeeping but does not show arbitrary write or UAF reclaim.
* Privileged kernel or device management state corruption path: +1. The affected state is inside GPUVM and TTM BO management, where wrong pinning can affect memory residency and mapping behavior.

Not awarded:

* Remote reachable: +0. No network path.
* Strong LPE plausibility: +0. No demonstrated reclaim, arbitrary write, callback control, or type confusion.
* Strong generic memory corruption: +0. The patch shows pin count underflow and state mismatch, not a concrete UAF, double free, or OOB write primitive.

## 3. Reachability analysis

The likely trigger is local access to AMD KFD or AMDGPU device interfaces. On many systems this may be available to users in render or video related groups, so PR:L is more appropriate than PR:H for practical triage. Containers may matter if GPU devices are passed through to a container or workload, but this is not a generic namespace escape path by itself. The issue requires AMDGPU KFD functionality and specific DOORBELL or MMIO remap BO handling, so exposure is hardware and configuration dependent but still reachable through ordinary GPU user interfaces when enabled.

Call-site confidence: high. The patch and trace show the affected free path, the EBUSY early return, and the later process teardown path that reaches ttm_bo_unpin.

## 4. Severity interpretation

This behaves above an ordinary low severity warning because a BO that remains mapped to GPU memory can lose its pin state and later be unpinned again. Realistic demonstrated impact is local DoS or GPU driver instability. Theoretical confidentiality or integrity impact is only weakly supported through GPU memory management state inconsistency, so this should not be treated as proven LPE. The paranoid score reaches Actionable Moderate because the bug affects lifetime and pinning semantics in a privileged device memory manager.

## 5. One-sentence report phrase

A local AMDGPU KFD user may trigger a double unpin of DOORBELL or MMIO remap BOs, causing TTM pin count underflow and possible GPU driver instability, with weak but review worthy concern around mapped GPU memory lifetime state.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED. YES REQUIRES MANUAL CHECK.

Reason: the demonstrated issue is not a proven privilege escalation, but it is a local GPU memory management lifetime bug involving pinned and mapped BO state, so it should not be auto-closed without checking whether premature unpin can affect residency, eviction, DMA visibility, or cross-process GPU memory isolation.

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

Patch: drm/amdkfd: Avoid double-unpin of DOORBELL/MMIO BOs on free [ Upstream
Commit: 461ae406ae12107ebb321cabe561434c27aaea58
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=461ae406ae12107ebb321cabe561434c27aaea58

Changed files:
  drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.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=461ae406ae12107ebb321cabe561434c27aaea58

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

The original Linux kernel CVE announcement for CVE-2026-80618 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80618

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:L/PR:L/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 6.6

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: 5

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 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).