[CVE-2026-93175][MODERATE REGULAR] drm/amd/display: Fix dangling pointer in CRTC reset function [ Upstream

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

CVE: CVE-2026-93175
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: drm/amd/display: Fix dangling pointer in CRTC reset function [ Upstream
Commit: 32bd68edbc6cbcfac0e4033b64f0bcadbf0efef5
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=32bd68edbc6cbcfac0e4033b64f0bcadbf0efef5
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93175
Analysis date: Thu, 17 Sep 2026 20:09:07 -0400
ActionableScore: 4
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-2026-93175 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93175

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-2026-93175	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-93175 CHECK WITH IMPACT FROM ORIG NN MODERATE	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-416;CWE-824;CWE-755;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A dangling pointer in the AMDGPU display CRTC reset path can occur because amdgpu_dm_crtc_reset_state frees the old CRTC state before allocating the replacement state. If allocation fails, crtc state can still point to freed memory and later DRM code may dereference stale state, creating a use-after-free condition. For the CVSS the PR:L is used because a local user with access to DRM or KMS control paths may be able to influence display state or memory pressure, while full administrator privileges are not necessarily required in all desktop or delegated GPU environments. The issue is not network reachable and requires local interaction with the graphics subsystem. Impact is at least local denial of service via kernel crash. In the paranoid interpretation, the UAF bug class may allow confidentiality or integrity impact if freed state memory is reused in a controllable way, so manual review is recommended.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4)  SKIP CVE-2026-93175 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	UAF HARDWARE  DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP	-	-	checked

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

ActionableScore=4
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=NO

1. ActionableScore

* Raw conservative score: 3
* Conservative score: 4
* Applied conservative floor: 3 -> 4 due to real UAF with stale active object pointer and no proven host-admin-only requirement.
* Raw paranoid score: 4
* Paranoid score: 4
* Final recommended bucket: **Borderline / manual review recommended**::

2. Signal breakdown

Positive signals:

* +2 Real UAF / lifetime violation. `amdgpu_dm_crtc_reset_state()` destroyed the old `crtc->state` before allocating the replacement state. If allocation failed, `crtc->state` still pointed to freed memory.
* +1 realistic kernel crash / DoS. A later DRM or AMDGPU path using `crtc->state` can dereference freed memory and crash the kernel.
* +1 paranoid weak active-object concern. The dangling pointer is left installed in an active DRM CRTC object rather than being limited to a local cleanup-only stale pointer. This supports manual review, but does not establish controlled reclaim or arbitrary read/write.

Non-awarded or withheld signals:

* Controlled reclaim not demonstrated.
* Arbitrary kernel read/write not demonstrated.
* Callback or function-pointer control not demonstrated.
* Confidentiality and integrity impact not awarded, because the patch establishes dangling state and possible UAF but not a concrete leak, write primitive, or privilege-escalation chain.
* Local unprivileged trigger not awarded, because the complete vulnerable CRTC reset path is not proven reachable by an ordinary user from the supplied evidence.
* Host-admin penalty not applied, because host-admin-equivalent privilege is also not positively established.
* Race penalty not applied, because this is an ordered allocation-failure lifetime bug, not a timing race.
* Rare hardware penalty not applied. AMDGPU/display hardware is hardware-specific but not automatically rare.
* Concrete repeated release/refcount signal not awarded. The patch shows one destroy/free followed by a stale published pointer, not a later second put/free/refcount mutation on the exact same reference.
* FLOOR 5 not applied. The stale object is active and structured, but attacker-controlled reclaim, attacker-shaped replacement, below-host-admin complete reachability, or another stronger exploitation surface is not established.

3. Reachability analysis

The vulnerable code is in the AMDGPU DRM display CRTC reset path. The immediate trigger requires `kzalloc_obj(*state)` failure after the old CRTC state has already been destroyed. A local actor may influence memory pressure, and DRM/KMS display state may be reachable through a compositor, DRM master, display server, or delegated graphics service, but the supplied patch does not prove that an ordinary logged-in user can force the complete vulnerable reset sequence.

Host administrator privilege is not positively established, so `HostAdminRequired=UNKNOWN` rather than `YES`. Below-host-admin reachability is also not positively established, so `HostAdminRequired=NO` is not used. Namespace-scoped privilege does not appear relevant for this DRM/KMS path, so `NamespaceScopedPrivilege=NO`.

There is no network reachability. There is no evidence of a namespace-based trigger. There is a hardware prerequisite in the sense that AMDGPU display code must be in use, but this is not treated as rare hardware. The main reliability constraint is allocation failure at a specific point in the reset path.

4. Primitive and severity interpretation

The exact primitive is a dangling pointer to freed `dm_crtc_state` / `drm_crtc_state` storage left in `crtc->state`. This is a real UAF candidate because the freed state remains externally reachable through the active CRTC object after the function returns.

This is an active structured object, not fixed stale DMA/USB storage. It is also not merely a local cleanup-only stale dereference, because the stale pointer remains installed in the CRTC object and may be consumed by later DRM/AMDGPU state handling. However, the patch does not show controlled reclaim, object replacement, attacker-controlled post-free contents, callback control, arbitrary write, information disclosure, or demonstrated LPE.

Primitive class is `CLASS_B`: a real kernel lifetime/UAF primitive exists, but the supplied evidence supports mainly crash/DoS and unresolved exploitation review rather than a strong Important-preserving primitive. `ImportantCandidate=NO` because the current evidence does not establish enough exploitation leverage beyond crash to call it a strong Important candidate. `AutoDowngradeAllowed=NO` because this is a concrete active-object UAF, not a harmless warning or pure resource leak, and automatic closure would risk losing a real lifetime bug that deserves human review.

Likely operational severity is borderline to actionable Moderate depending on product exposure and whether the CRTC reset path can be reached below host admin.

5. One-sentence report phrase

A dangling pointer in the AMDGPU CRTC reset path can leave `crtc->state` pointing to freed memory after allocation failure, creating a local UAF risk that can cause kernel DoS and should be manually reviewed for possible exploitation beyond crash.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: the patch establishes a real dangling pointer / UAF condition in an active DRM state object, but does not establish controlled reclaim, arbitrary read/write, privilege escalation, or a complete below-host-admin trigger path.

7. Call-site confidence

Call-site confidence: medium

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

Patch: drm/amd/display: Fix dangling pointer in CRTC reset function [ Upstream
Commit: 32bd68edbc6cbcfac0e4033b64f0bcadbf0efef5
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=32bd68edbc6cbcfac0e4033b64f0bcadbf0efef5

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=32bd68edbc6cbcfac0e4033b64f0bcadbf0efef5

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

The original Linux kernel CVE announcement for CVE-2026-93175 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93175

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:H/PR:L/UI:N/S:U/C:N/I:N/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: unknown
  Paranoid ActionableScore: 4

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).