[CVE-2026-43444][LOW] drm/amdkfd: Unreserve bo if queue update failed [ Upstream

[CVE-2026-43444][LOW] drm/amdkfd: Unreserve bo if queue update failed [ Upstream

[AL-KERNEL]

CVE: CVE-2026-43444
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: drm/amdkfd: Unreserve bo if queue update failed [ Upstream
Commit: 781110700ada22168fbb490dd61432d23a17a5b4
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=781110700ada22168fbb490dd61432d23a17a5b4
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-43444
Analysis date: Sat, 01 Aug 2026 12:07:41 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A missing BO unreserve in the AMD KFD queue update error path can leave the VM root buffer object reserved after validation failure, allowing a local GPU device user to cause a denial of service in the GPU compute stack without evidence of privilege escalation or information disclosure.

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

The original Linux kernel CVE announcement for CVE-2026-43444 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-43444

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-2026-43444	LOW	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';*CWE-772;CWE-667;CWE-755;BEST CVSS score: '5.5';DESCR 'A missing cleanup in the AMD KFD queue update error path can leave the VM root buffer object reserved when validation of a user queue update fails. A local process with access to the KFD GPU device can trigger the failure by requesting a queue update whose ring buffer is not mapped on the GPU, causing the function to return while the BO reservation is still held. This can block later GPU VM or queue operations that need the same reservation and may result in a persistent local denial of service for the GPU compute stack. For the CVSS the PR:L is used because reliable triggering requires local code execution with access to /dev/kfd or the relevant GPU device permissions, but not full administrator privileges. The issue is not network reachable. Impact is availability loss only, with no supported evidence of information disclosure or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2) 	MAYBE	SIMPLEFIX ERRORPATH HARDWARE  INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	-	-	checked

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

ActionableScore=2

## 1. ActionableScore

* Conservative score: **2**
* Paranoid score: **2**
* Final recommended bucket: **Ordinary Moderate / Low-like**

## 2. Signal breakdown

Triggered signals:

* **Local unprivileged trigger: +1**
  A local process with access to `/dev/kfd` or relevant AMD GPU device permissions can likely trigger the failed queue update path. This is not full root or CAP_SYS_ADMIN in typical GPU compute deployments.

* **Reliable local DoS / resource-lock DoS: +1**
  Missing `amdgpu_bo_unreserve(vm->root.bo)` can leave the VM root BO reserved after returning `-EFAULT`, potentially blocking later GPU VM or queue operations that need the same reservation.

Not triggered:

* **Generic memory corruption: +0**
  The patch shows a missing cleanup/unreserve in an error path, not UAF, OOB write, double-free, type confusion, or arbitrary write.

* **Privilege escalation plausible: +0**
  No supported LPE primitive is visible. The issue is a stuck reservation/resource cleanup bug.

* **Confidentiality / Integrity impact: +0**
  No information disclosure, policy bypass, or data corruption primitive is indicated.

* **Remote reachable: +0**
  This is a local GPU device/API path, not network reachable.

* **Admin/root required penalty: +0**
  Access to KFD may require device permissions or group membership, but not necessarily full host-root. I would not apply the full `-2` admin penalty.

Call-site confidence: **medium**. The shown error path is clear, but broader caller behavior and exact lock persistence are inferred from normal AMDGPU BO reservation semantics rather than fully visible in the provided patch.

## 3. Reachability analysis

The likely trigger is a local process using AMD KFD queue update functionality with an invalid or unmapped ring buffer address or size. In practical deployments, this requires access to AMD GPU compute device nodes such as `/dev/kfd` and related DRM render devices. Containers may expose these devices to workloads, so this can be reachable by non-root users inside GPU-enabled compute containers if device access is delegated.

The path is not network reachable. It is also hardware and configuration dependent because it requires an AMD GPU with KFD enabled and accessible to the attacker. Realistic exploitation conditions are plausible for local GPU compute users, but the demonstrated impact is limited to GPU driver or compute-stack denial of service.

## 4. Severity interpretation

This behaves like an **ordinary Moderate / Low-like local DoS**, not an Important-class vulnerability. The patch fixes a missing cleanup operation on an error path and does not show memory corruption, object reuse, attacker-controlled overwrite, fd theft, namespace escape, or privilege escalation.

Theoretical impact is a persistent reservation/lock state that can disrupt GPU queue or VM operations. Realistic evidence supports availability impact only. It should not be auto-promoted to Important based solely on the fact that the bug is in a kernel GPU driver.

## 5. One-sentence report phrase

A missing BO unreserve in the AMD KFD queue update error path can leave the VM root buffer object reserved after validation failure, allowing a local GPU device user to cause a denial of service in the GPU compute stack without evidence of privilege escalation or information disclosure.

## 6. Manual review recommendation

**NO MANUAL CHECK NEEDED**

This can be handled as an auto-closable local DoS/resource cleanup issue unless the target environment exposes `/dev/kfd` broadly to untrusted multi-tenant GPU workloads where GPU availability is mission critical.

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

Patch: drm/amdkfd: Unreserve bo if queue update failed [ Upstream
Commit: 781110700ada22168fbb490dd61432d23a17a5b4
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=781110700ada22168fbb490dd61432d23a17a5b4

Changed files:
  drivers/gpu/drm/amd/amdkfd/kfd_process_queue_manager.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=781110700ada22168fbb490dd61432d23a17a5b4

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

The original Linux kernel CVE announcement for CVE-2026-43444 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-43444

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:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.5

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