[CVE-2026-68238][LOW] drm/amdgpu: Release VFCT ACPI table reference

[CVE-2026-68238][LOW] drm/amdgpu: Release VFCT ACPI table reference

[AL-KERNEL]

CVE: CVE-2026-68238
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: drm/amdgpu: Release VFCT ACPI table reference
Commit: 312278b3091912fa56a6a587609f17dcb33465c2
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=312278b3091912fa56a6a587609f17dcb33465c2
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68238
Analysis date: Mon, 10 Aug 2026 18:35:00 -0400
ActionableScore: 1
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like. Auto-close candidate
Manual review required: NO

Summary:
A missing acpi_put_table in the amdgpu VFCT BIOS path can leak ACPI table references and mappings during repeated driver lifecycle operations, but exploitation typically requires administrative control and the impact is limited to resource exhaustion DoS.

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

The original Linux kernel CVE announcement for CVE-2026-68238 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68238

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
======================================================================

CVE-2026-68238	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:H/UI:N/S:U/C:N/I:N/A:H';*CWE-401;*CWE-772;CWE-404;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.4';DESCR 'amdgpu_acpi_vfct_bios can leak an ACPI VFCT table reference because acpi_get_table is not paired with acpi_put_table on several exit paths. Each call can keep the table validation reference and mapping alive, so repeated driver initialization or recovery cycles may gradually consume kernel resources. For the CVSS the PR:H is used because reliable triggering normally requires administrative control over the GPU driver or device lifecycle. The issue is not network reachable and does not provide a clear memory corruption primitive. Impact is resource exhaustion and denial of service only, with no supported confidentiality or integrity impact.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like. Auto-close candidate (with actual score 1)  SKIP CVE-2026-68238 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	SIMPLEFIX LEAK 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. Auto-close candidate**

## 2. Signal breakdown

Triggered signals:

* Availability impact realistic: +1
  Repeated calls can leak ACPI table references and mappings, so sustained repeated driver lifecycle operations could gradually consume kernel resources.

* Broad/default/common subsystem or broadly deployed exposure: +1
  amdgpu is a common GPU driver on AMD systems, but this does not imply easy attacker reachability.

Subtracted signals:

* Requires admin/root/CAP in typical deployments: -2
  Reliable triggering normally requires control over GPU driver initialization, reload, bind/unbind, recovery, or similar device lifecycle operations.

Not triggered:

* No remote reachable signal. This is not network-triggerable.
* No local unprivileged trigger shown.
* No generic memory corruption. The patch fixes a missing acpi_put_table after acpi_get_table.
* No UAF, double-free, OOB write, type confusion, refcount takeover, or arbitrary write shown.
* No confidentiality or integrity impact supported.
* No practical privilege escalation path supported.

## 3. Reachability analysis

The affected function is in the amdgpu BIOS discovery path and is reached during GPU driver initialization or related device lifecycle handling. In normal deployments, an attacker would need administrative control over the driver or device state to trigger repeated calls reliably. Namespaces or containers do not materially lower the privilege requirement unless a highly unusual setup delegates real host GPU driver lifecycle control to an untrusted workload. The path may exist on many AMD GPU systems, but exposure is local and privileged, not remote or packet-driven.

Call-site confidence: medium. The patch context and function name clearly indicate driver BIOS initialization behavior, but full caller context is not included.

## 4. Severity interpretation

This behaves like a low-end resource leak issue rather than an Important-class vulnerability. The realistic impact is gradual kernel resource leakage and possible denial of service only after repeated privileged triggering. The theoretical worst case is stronger availability impact if an administrator-controlled loop repeatedly forces the path, but there is no evidence of memory corruption, sensitive data exposure, permission bypass, or privilege escalation.

## 5. One-sentence report phrase

A missing acpi_put_table in the amdgpu VFCT BIOS path can leak ACPI table references and mappings during repeated driver lifecycle operations, but exploitation typically requires administrative control and the impact is limited to resource exhaustion DoS.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This is a paired get/put resource leak in a privileged driver initialization path, with no concrete corruption primitive and no unprivileged or remote trigger shown.

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

Patch: drm/amdgpu: Release VFCT ACPI table reference
Commit: 312278b3091912fa56a6a587609f17dcb33465c2
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=312278b3091912fa56a6a587609f17dcb33465c2

Commit description:

amdgpu_acpi_vfct_bios() fetches the VFCT table with acpi_get_table()
but never releases it. acpi_get_table() takes a reference on the
table (incrementing its validation_count and mapping it on the 0->1
transition); without a paired acpi_put_table() the mapping is leaked
on every call, whether or not a matching VBIOS image is found.

Route all exit paths after the table is acquired through a common
acpi_put_table(). The VBIOS image is copied out with kmemdup() before
the table is released, so it remains valid for the caller.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patch.msgid.link/20260708193518.702584-3-mario.limonciello@amd.com
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit ca59886 )
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/amd/amdgpu/amdgpu_bios.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=312278b3091912fa56a6a587609f17dcb33465c2

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

The original Linux kernel CVE announcement for CVE-2026-68238 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68238

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:H/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.4

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).