[CVE-2026-80540][MODERATE 7.0] drm/amdgpu: Fix UVD decode image min size calculation

[CVE-2026-80540][MODERATE 7.0] drm/amdgpu: Fix UVD decode image min size calculation

[AL-KERNEL]

CVE: CVE-2026-80540
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: drm/amdgpu: Fix UVD decode image min size calculation
Commit: bc7397a033ac52f6d8c9bb6510d61694b2a3fce7
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bc7397a033ac52f6d8c9bb6510d61694b2a3fce7
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80540
Analysis date: Wed, 26 Aug 2026 12:24:38 -0400
ActionableScore: 7
ActionableScore lower bound: 5
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-80540 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80540

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-80540	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:H/I:H/A:H';CWE-131;*CWE-787;CWE-190;*CWE-20;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'AMDGPU UVD decode validation used width instead of pitch when calculating the minimum image buffer size and also allowed pitch values above 4096. A local user with access to the DRM render node can submit a crafted UVD decode command stream where pitch is larger than width, causing the driver to accept a target buffer that may be too small for the decoder output. This creates a plausible GPU DMA out of bounds write or memory overwrite condition, with likely effects ranging from GPU reset or kernel crash to corruption of adjacent GPU mapped memory. For the CVSS the PR:L is used because DRM render node access is commonly available to non root local users or service accounts and does not require full administrator privileges. The issue is not network reachable and exploitation requires local access to the GPU device. Impact is at least local denial of service and in the paranoid case may include confidentiality or integrity impact due to memory corruption, so manual review is recommended.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7)  SKIP CVE-2026-80540 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	SIMPLEFIX HARDWARE  KPANIC INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN6 DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=7
ActionableScoreLower=5

1. ActionableScore
* Conservative score: 5
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

2. Signal breakdown
* Local unprivileged trigger: +1. DRM render nodes are commonly available to local non-root users on desktop or GPU-enabled systems.
* Constrained kernel/GPU buffer overwrite: +1 conservative. The validation used width instead of pitch, so an undersized decode target buffer could be accepted. The overwrite path is plausible, but payload and target control are not clearly demonstrated.
* Memory layout invariant restoration: +1. The patch restores consistency between pitch, height, and the minimum image buffer size, and rejects pitch above 4096 to avoid overflow.
* Privileged kernel/device-management memory corruption path: +1. The bug is in GPU command validation before UVD decode hardware or firmware consumes the buffer layout.
* Reliable kernel crash / strong DoS: +1. A bad decode buffer layout can plausibly cause GPU fault, GPU reset, driver failure, or kernel crash.
* Paranoid generic memory corruption: +2. In the higher interpretation, accepting a too-small decode target can become a GPU DMA-style out-of-bounds write into adjacent GPU-mapped memory.
* Weak LPE concern: +1 paranoid only. Local privilege escalation is not demonstrated, but GPU memory corruption from a local render-node API is enough to require manual review.
* Confidentiality impact plausible: +1 paranoid only. Adjacent GPU memory corruption or stale GPU-visible data exposure is plausible but not proven.
* Integrity impact plausible: +1 paranoid only. Corruption of adjacent GPU-mapped buffers is the main concern.
* Constrained primitive uncertainty: -1. The patch does not show attacker-controlled arbitrary write, reliable reclaim, or direct kernel object overwrite.
* Hardware/subsystem dependency: -1 paranoid balancing factor. The path requires AMDGPU UVD decode support and access to the relevant GPU device.

3. Reachability analysis
A local user with access to the AMDGPU DRM render node can potentially submit a crafted UVD decode command stream with pitch larger than width. This usually does not require full root privileges, because render-node access is often granted to desktop sessions, video/render groups, or GPU-enabled service accounts. The issue is not network reachable. Containers matter if the host passes through /dev/dri/renderD* or equivalent GPU device access, because a container user may then reach the same command submission path. The path is hardware and driver dependent, but AMDGPU render-node usage is common enough that it should not be treated as obscure.

4. Severity interpretation
This is stronger than an ordinary Moderate validation bug because the corrected value controls a buffer-size check before GPU decode output. Conservative handling is Actionable Moderate because the demonstrated primitive is an undersized GPU decode target that can plausibly cause DoS and constrained memory corruption. The Important-class interpretation is defensible for manual triage because GPU DMA-adjacent out-of-bounds writes from a local render-node API can sometimes become integrity or privilege-boundary issues, even though this patch alone does not demonstrate arbitrary code execution or a reliable LPE chain.

5. One-sentence report phrase
AMDGPU UVD decode validation used width instead of pitch for the minimum image buffer size, allowing a local render-node user to submit a crafted decode command that may accept an undersized target buffer and cause GPU memory corruption or DoS.

6. Manual review recommendation
MANUAL CHECK REQUIRED. YES REQUIRES MANUAL CHECK.
Reason: the patch is a small validation fix, but the affected value is a decode target buffer size used by GPU hardware or firmware, making constrained OOB write and possible GPU memory corruption plausible enough for manual security review.

Call-site confidence: medium. The provided patch shows the vulnerable validation site and the corrected buffer-size calculation, but not all downstream UVD buffer validation and GPU VM mapping behavior.

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

Patch: drm/amdgpu: Fix UVD decode image min size calculation
Commit: bc7397a033ac52f6d8c9bb6510d61694b2a3fce7
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bc7397a033ac52f6d8c9bb6510d61694b2a3fce7

Commit description:

This needs to use pitch instead of width. Also reject pitch
over 4096 to avoid overflow.

Signed-off-by: David Rosca <david.rosca@amd.com>
Acked-by: Leo Liu <leo.liu@amd.com>
Reviewed-by: Ruijing Dong <ruijing.dong@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit b41c8cb )
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/amd/amdgpu/amdgpu_uvd.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=bc7397a033ac52f6d8c9bb6510d61694b2a3fce7

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

The original Linux kernel CVE announcement for CVE-2026-80540 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80540

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:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 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: 5
  Paranoid ActionableScore: 7

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: YES
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).