[CVE-2026-80539][MODERATE REGULAR] drm/amdgpu: disallow multiple FENCE chunks in one submit

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-80539
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: drm/amdgpu: disallow multiple FENCE chunks in one submit
Commit: 070229262ede37d17c4ea596650deb6e5eb5d106
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=070229262ede37d17c4ea596650deb6e5eb5d106
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80539
Analysis date: Wed, 26 Aug 2026 11:38:59 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Ordinary Moderate / Low-like, not an Important candidate
Manual review required: NO

Summary:
AMDGPU command submission allowed duplicate FENCE chunks to overwrite a single stored BO reference without releasing the previous one, allowing a local DRM user to leak BO references across process exit and potentially cause resource exhaustion DoS.

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

The original Linux kernel CVE announcement for CVE-2026-80539 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80539

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 REGULAR
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
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CVE-2026-80539	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:N/I:N/A:H';*CWE-772;*CWE-401;**CWE-400;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'AMDGPU command submission allowed more than one FENCE chunk in a single submit while p uf_bo is only a single slot. A second FENCE chunk could overwrite the previous BO reference without dropping it, so every FENCE chunk except the last one could leak a BO reference that survives handle close and process exit. For the CVSS the PR:L is selected because reliable triggering requires local access to the DRM AMDGPU submission interface, typically through a render node or a user in a graphics capable group. The issue is not network reachable and is triggered through a local GPU ioctl path rather than packet traffic. Impact is denial of service through resource exhaustion. There is no concrete UAF, OOB access, arbitrary write, information leak, or privilege escalation primitive supported by this patch context.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like, not an Important candidate (with actual score 3)  SKIP CVE-2026-80539 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	SIMPLEFIX LEAK HARDWARE  INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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

ActionableScore=3
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 3
* Final recommended bucket: **Ordinary Moderate / Low-like, not an Important candidate**::

## 2. Signal breakdown

* Local unprivileged trigger: +1
  Triggering is through the local AMDGPU command submission ioctl path. On many systems this is reachable by users with access to `/dev/dri/renderD*` or a graphics-capable group.

* Availability impact realistic: +1
  Duplicate FENCE chunks can leak BO references that survive handle close and process exit. Repeated submissions can plausibly exhaust GPU or kernel resources.

* Reliable kernel crash / strong DoS: +1 only for paranoid score
  The patch supports sustained resource exhaustion, but not an immediate single-shot crash. This is why it is counted only in the paranoid score.

* No generic memory corruption: +0
  The bug is a BO reference leak caused by overwriting `p->uf_bo` without dropping the previous reference. The patch does not show UAF, double free, OOB access, arbitrary write, type confusion, or attacker-controlled reuse.

* No privilege escalation plausible: +0
  There is no supported LPE primitive. The impact is resource exhaustion only.

* No confidentiality or integrity impact: +0
  No information disclosure, unauthorized write, page-cache corruption, or security-boundary bypass is indicated.

## 3. Reachability analysis

A local user or process with access to the AMDGPU DRM submission interface can submit multiple `AMDGPU_CHUNK_ID_FENCE` chunks in one command submission. This is not network reachable. Containers only matter if the DRM device node is passed through and accessible inside the container. The affected path is relevant on systems using AMDGPU, but it is hardware-specific rather than a universal kernel interface.

Call-site confidence: high. The commit message explains the lifetime consequence directly: `amdgpu_cs_p1_user_fence()` takes BO references, `p->uf_bo` is single-slot, and `amdgpu_cs_parser_fini()` only releases the final value.

## 4. Severity interpretation

This behaves like a local resource leak leading to potential DoS, not like memory corruption or privilege escalation. The conservative interpretation is ordinary Moderate or Low-like because exploitation requires repeated local GPU submissions and only affects availability. The paranoid interpretation raises practical concern slightly because the leaked BO references survive process exit, making sustained resource exhaustion plausible.

## 5. One-sentence report phrase

AMDGPU command submission allowed duplicate FENCE chunks to overwrite a single stored BO reference without releasing the previous one, allowing a local DRM user to leak BO references across process exit and potentially cause resource exhaustion DoS.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This is a reference leak/resource exhaustion issue without a concrete memory corruption, privilege escalation, confidentiality, or integrity primitive. It can be handled as non-urgent unless local GPU resource exhaustion is especially sensitive in the target environment.

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

Patch: drm/amdgpu: disallow multiple FENCE chunks in one submit
Commit: 070229262ede37d17c4ea596650deb6e5eb5d106
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=070229262ede37d17c4ea596650deb6e5eb5d106

Commit description:

amdgpu_cs_pass1() dispatches on chunk_id once per chunk without
rejecting repeated ids. p->uf_bo is a single-slot field, so a
submission carrying two AMDGPU_CHUNK_ID_FENCE chunks runs
amdgpu_cs_p1_user_fence() twice, and the second run overwrites
p->uf_bo with a freshly referenced BO without dropping the reference
taken by the first.

amdgpu_cs_parser_fini() only unrefs the final p->uf_bo, so every FENCE
chunk but the last leaks a BO reference. The leaked BO outlives handle
close and process exit.

Reject duplicate FENCE chunks the same way commit fec5f8e
("drm/amdgpu: disallow multiple BO_HANDLES chunks in one submit") did
for p->bo_list.

Fixes: d38ceaf ("drm/amdgpu: add core driver (v4)")
Reported-by: Yuhao Jiang <danisjiang@gmail.com>
Assisted-by: Claude:claude-opus-5
Cc: stable@vger.kernel.org
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Junrui Luo <moonafterrain@outlook.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 665b1fc )
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=070229262ede37d17c4ea596650deb6e5eb5d106

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

The original Linux kernel CVE announcement for CVE-2026-80539 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80539

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: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: 2
  Paranoid ActionableScore: 3

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 REGULAR

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).