[CVE-2026-80576][MODERATE 7.0] drm/amdgpu: reject oversized IBs with per-ring packet limits

[CVE-2026-80576][MODERATE 7.0] drm/amdgpu: reject oversized IBs with per-ring packet limits

[AL-KERNEL]

CVE: CVE-2026-80576
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: drm/amdgpu: reject oversized IBs with per-ring packet limits
Commit: 6e164ba1057175fb8a370d8e05cbff5c57eac0c8
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6e164ba1057175fb8a370d8e05cbff5c57eac0c8
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80576
Analysis date: Wed, 26 Aug 2026 13:54:00 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
An oversized user supplied IB length in amdgpu command submission can corrupt adjacent GPU packet control bits and destabilize command submission, requiring local DRM device access and primarily causing GPU hang or denial of service.

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

The original Linux kernel CVE announcement for CVE-2026-80576 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80576

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-2026-80576	MODERATE	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:L/I:L/A:H';*CWE-20;CWE-190;CWE-1284;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H';BEST CVSS score: '6.6';DESCR 'An oversized user supplied IB length in the amdgpu command submission path can exceed the packet size field supported by the selected ring type. When ring_emit_ib encodes this length into a hardware packet, high bits of the length can corrupt adjacent control bits and destabilize command submission. For the CVSS the PR:L is used because a local user with access to the DRM render or GPU device node can submit command streams in common desktop and compute deployments. The issue is not network reachable and requires local code execution or a local process context. Impact is primarily denial of service through GPU hang, reset, or wider system instability. Limited confidentiality or integrity impact is kept only for the paranoid score because the bug affects GPU packet control fields, but the patch does not show a direct CPU kernel memory corruption primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)  SKIP CVE-2026-80576 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	HARDWARE PACKET  INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP	-	-	checked

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

ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: **4**
* Paranoid score: **5**
* Final recommended bucket: **Actionable Moderate at minimum**

## 2. Signal breakdown

Conservative signals:

* **Local unprivileged trigger: +1**. The path is the amdgpu command submission ioctl path, commonly reachable by a local user with access to DRM render or GPU device nodes.
* **Memory corruption, weak/indirect corruption candidate: +1**. The user supplied IB length can exceed the packet field width and corrupt adjacent GPU packet control bits, but the patch does not show CPU kernel memory corruption, UAF, type confusion, or arbitrary write.
* **Reliable kernel crash / strong DoS: +1**. The commit explicitly says oversized values can destabilize command submission, which plausibly means GPU hang, reset, or broader system instability.
* **Integrity impact plausible: +1**. The affected value can corrupt command submission control bits, so limited integrity impact is plausible inside the GPU command stream.

Paranoid additional signal:

* **Broad/default/common subsystem exposure: +1**. amdgpu render node access is common on AMD desktop, workstation, and GPU compute systems, and command submission is a normal local data path.

Signals not awarded:

* **No remote reachable signal**. The bug is not network-triggerable.
* **No strong LPE signal**. The patch does not show reclaim, attacker-controlled object replacement, function pointer corruption, arbitrary write, or CPU kernel memory corruption.
* **No high-control API bonus**. DRM GPU ioctls are rich device APIs, but this patch only shows oversized packet length validation and not control over kernel object lifetime, allocator layout, refcounts, DMA ownership, or callback targets.

## 3. Reachability analysis

A local process that can submit amdgpu command streams can potentially trigger the bug by providing an oversized IB length. In typical desktop or GPU compute deployments, DRM render nodes may be accessible to ordinary users or to users in render or video related groups, so **PR:L** is more appropriate than **PR:H** for practical triage.

Containers can matter if `/dev/dri/renderD*` or card nodes are passed into the container. Without GPU device node access, the issue is not reachable. The path is not remotely reachable by packets or network protocol parsing.

## 4. Severity interpretation

This behaves above an ordinary low-risk validation bug because the invalid user-controlled length is encoded into hardware packet fields and can corrupt adjacent command submission control bits. Realistic impact is primarily local DoS through GPU hang, GPU reset, or system instability.

The theoretical risk is higher than simple DoS because command submission control corruption may have hardware and memory-management side effects depending on ring type and mapping context. However, the patch does not support classifying this as strong kernel memory corruption or confirmed privilege escalation. Therefore the conservative score is borderline manual-review, and the paranoid score is **Actionable Moderate** rather than **Strong Important**.

## 5. One-sentence report phrase

An oversized user supplied IB length in amdgpu command submission can corrupt adjacent GPU packet control bits and destabilize command submission, requiring local DRM device access and primarily causing GPU hang or denial of service.

## 6. Manual review recommendation

**MANUAL CHECK REQUIRED. YES REQUIRES MANUAL CHECK.**

Reason: this is a user-reachable GPU command submission validation issue with corruption of packet control bits. It is not proven LPE, but it is not safe to auto-close because GPU packet encoding bugs can have device-specific side effects beyond a simple validation failure.

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

Patch: drm/amdgpu: reject oversized IBs with per-ring packet limits
Commit: 6e164ba1057175fb8a370d8e05cbff5c57eac0c8
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6e164ba1057175fb8a370d8e05cbff5c57eac0c8

Commit description:

On GFX rings, amdgpu_cs_p2_ib() passed user-supplied ib_bytes through
to ib->length_dw without a limit, while ring_emit_ib() encodes length
into packet fields. Oversized values can corrupt adjacent control bits
and destabilize command submission.

Add a per-ring IB packet size limit helper and reject command
submissions exceeding the corresponding dword limit before IB
allocation. Use the documented 20-bit limit for GFX/compute/SDMA/VPE,
and apply the MM fallback limit for other ring types.

Signed-off-by: Candice Li <candice.li@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 7f48fa2 )
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/amd/amdgpu/amdgpu_cs.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=6e164ba1057175fb8a370d8e05cbff5c57eac0c8

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

The original Linux kernel CVE announcement for CVE-2026-80576 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80576

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:L/A:H
  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: 4
  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).