[CVE-2026-80542][MODERATE REGULAR] drm/amd/display: Fix NULL pointer dereference in amdgpu_dm_crtc_set_vblank()

[CVE-2026-80542][MODERATE REGULAR] drm/amd/display: Fix NULL pointer dereference in amdgpu_dm_crtc_set_vblank()

[AL-KERNEL]

CVE: CVE-2026-80542
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: drm/amd/display: Fix NULL pointer dereference in amdgpu_dm_crtc_set_vblank()
Commit: 5045fb4c70bfde36a05e0f41cf35ddfb6d85d3af
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5045fb4c70bfde36a05e0f41cf35ddfb6d85d3af
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80542
Analysis date: Wed, 26 Aug 2026 12:55:37 -0400
ActionableScore: 3
ActionableScore lower bound: unknown
Actionable bucket: Borderline, manual review recommended
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-80542 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80542

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: YES

A detailed explanation of the methodology and priority rules is included
at the end of this message.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-80542	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	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-476;CWE-754;*CWE-20;BEST CVSS score: '5.5';DESCR 'A NULL-pointer dereference in the AMDGPU display vblank path occurs because amdgpu_dm_crtc_set_vblank() can dereference acrtc_state stream before a stream is attached to the CRTC state. A local process with access to the DRM device can trigger this through DRM_IOCTL_MODE_CRTC_GET_SEQUENCE when vblank is enabled or queried at the wrong display state, causing a kernel crash (DoS). For the CVSS the PR:L is used because triggering requires local code execution and access to the DRM device node, but not full administrative privileges. The issue is not network reachable and is tied to local graphics control paths rather than packet or remote protocol input. Impact is denial of service only because the patch indicates a NULL dereference and does not show a UAF, OOB write, information leak, or privilege escalation primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 3)  SKIP CVE-2026-80542 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	DANGER NULLPTR SIMPLEFIX HARDWARE TEST 	-	-	checked

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

ActionableScore=3

1. ActionableScore
* Conservative score: 3
* Paranoid score: 3
* Final recommended bucket: **Borderline, manual review recommended**::

2. Signal breakdown
* Local unprivileged trigger: +1. A local process with access to the DRM device node can reach `DRM_IOCTL_MODE_CRTC_GET_SEQUENCE`.
* Reliable kernel crash / strong DoS: +1. The commit shows a concrete NULL pointer dereference and kernel crash path.
* Broad/default/common subsystem or broadly deployed exposure: +1. AMDGPU DRM is a common local graphics stack path on affected systems.
* No generic memory corruption bonus. The patch shows a NULL dereference, not UAF, OOB write, type confusion, refcount misuse, or attacker-controlled overwrite.
* No privilege escalation bonus. There is no supported LPE primitive.
* No network reachability bonus. This is a local DRM ioctl path.

3. Reachability analysis
The bug is triggered locally through DRM ioctl access, specifically via the vblank sequence query path before `acrtc_state->stream` is attached. Typical desktop or GPU compute systems may allow non-root users access to DRM device nodes through local seat/session permissions or render/video groups, so PR:L is the practical CVSS interpretation. Containers usually do not get direct DRM device access unless explicitly passed through. The path is not network reachable and requires affected AMDGPU display hardware and driver state.

4. Severity interpretation
This behaves like an actionable local DoS rather than an Important-class vulnerability. The demonstrated impact is a kernel NULL pointer dereference and crash. Theoretical escalation is not supported because the patch does not indicate UAF, stale object reuse, writable corruption, callback control, or an arbitrary read/write primitive. It should not be auto-promoted to memory corruption, but the local unprivileged DRM ioctl reachability makes manual triage reasonable.

5. One-sentence report phrase
A local NULL-pointer dereference in the AMDGPU display vblank path can be triggered through DRM_IOCTL_MODE_CRTC_GET_SEQUENCE before a stream is attached to the CRTC state, causing a kernel crash (DoS) without evidence of privilege escalation.

6. Manual review recommendation
MANUAL CHECK RECOMMENDED.
Reason: local DRM ioctl reachability and kernel crash are concrete, but the bug is NULL dereference only and does not show a memory corruption or LPE primitive.

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

Patch: drm/amd/display: Fix NULL pointer dereference in amdgpu_dm_crtc_set_vblank()
Commit: 5045fb4c70bfde36a05e0f41cf35ddfb6d85d3af
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5045fb4c70bfde36a05e0f41cf35ddfb6d85d3af

Commit description:

amdgpu_dm_crtc_set_vblank() dereferences acrtc_state->stream when
vblank is enabled/queried from DRM_IOCTL_MODE_CRTC_GET_SEQUENCE before
a stream is attached to it.

BUG: kernel NULL pointer dereference, address: 0000000000000008
RIP: amdgpu_dm_crtc_set_vblank+0x6b/0x4d0 [amdgpu]
Call Trace:
 drm_vblank_enable
 drm_vblank_get
 drm_crtc_get_sequence_ioctl
 drm_ioctl_kernel
 drm_ioctl

Reproduced by running VKCTS with WSI tests enabled on RADV.

Guard the enable path on acrtc_state->stream being non-NULL, matching
the existing checks in this function.

Fixes: 34d66bc ("drm/amd/display: Fix Xorg desktop unresponsive on Replay panel")
Reviewed-by: Melissa Wen <mwen@igalia.com>
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 7b1b31b )
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crtc.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=5045fb4c70bfde36a05e0f41cf35ddfb6d85d3af

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

The original Linux kernel CVE announcement for CVE-2026-80542 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80542

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: 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).