[CVE-2026-53285][LOW] drm/amd/display: Wrap DCN32 phantom-plane allocation in DC_RUN_WITH_PREEMPTION_ENABLED

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

CVE: CVE-2026-53285
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: drm/amd/display: Wrap DCN32 phantom-plane allocation in DC_RUN_WITH_PREEMPTION_ENABLED
Commit: 30bb2ec6695d62f63db4aa6179c4626834ed0cd6
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=30bb2ec6695d62f63db4aa6179c4626834ed0cd6
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53285
Analysis date: Fri, 26 Jun 2026 16:08:54 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A local denial of service can occur on affected AMD DCN32 display systems because phantom-plane allocation may enter the vmalloc path while local softirqs are disabled, triggering BUG_ON(in_interrupt()) and crashing the kernel.

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

The original Linux kernel CVE announcement for CVE-2026-53285 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53285

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: LOW
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-2026-53285	LOW	CHECK	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-667;CWE-754;CWE-755;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'A kernel crash can occur in the AMD DCN32 display path because dcn32_enable_phantom_plane may allocate a large dc_plane_state object while bandwidth validation is running inside a DC_FP_START region with local softirqs disabled. The allocation can enter the vmalloc path and hit BUG_ON(in_interrupt()), causing a local denial of service. For the CVSS the PR:L is used for the paranoid score because a local user or graphics session with access to DRM/KMS display control may be able to trigger display mode validation without full administrator privileges. The issue is not network reachable and does not show a UAF, OOB access, or arbitrary write primitive. Impact is denial of service via kernel crash only.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)  SKIP CVE-2026-53285  SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	DANGER SIMPLEFIX HARDWARE  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	-	-	checked

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

ActionableScore=2
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. A local graphical user or compositor with DRM/KMS display-control access may be able to trigger bandwidth validation and phantom-plane creation without full administrator privileges.
* Reliable kernel crash / strong DoS: +1. The commit explicitly describes `BUG_ON(in_interrupt())` through the `vmalloc` path, causing a kernel crash.
* Hard or configuration-specific trigger: -1. Triggering depends on AMD DCN32/321 display paths, phantom-plane allocation, DML1 validation, and the allocation occurring inside the FPU softirq-disabled region.
* Rare or hardware-specific exposure: -1. The issue is limited to affected AMD display hardware and specific display-core code paths.

Paranoid additional interpretation:

* Availability impact realistic: +1. If the affected display configuration is present and the mode-validation path is reachable from a local session, the crash is host-wide and may be reproducible.

No memory-corruption signals apply:

* No UAF, double-free, OOB write, arbitrary write, page-cache corruption, or lifetime-reclaim primitive is indicated.
* This is an invalid execution-context / locking-context bug leading to BUG/panic, not a demonstrated privilege-escalation primitive.

## 3. Reachability analysis

The bug is local, not network reachable. The likely trigger is a local user-space graphics path that causes DRM/KMS display mode validation on affected AMD DCN32/321 hardware. In typical desktop deployments, a logged-in graphical user or compositor may have enough access to exercise display configuration paths, so PR:L is more appropriate than PR:H for practical triage. Containers usually do not matter unless DRM devices are passed through. The path is not broadly default-exposed across all Linux systems because it depends on specific AMD display hardware and display configuration behavior.

## 4. Severity interpretation

This behaves like an ordinary Moderate / Low-like kernel DoS rather than an Important-class vulnerability. The realistic impact is a local kernel crash. The theoretical risk does not extend to privilege escalation based on the patch, because the failure mode is `BUG_ON(in_interrupt())` during allocation from an invalid context, with no evidence of attacker-controlled memory corruption or object lifetime abuse.

## 5. One-sentence report phrase

A local denial of service can occur on affected AMD DCN32 display systems because phantom-plane allocation may enter the vmalloc path while local softirqs are disabled, triggering BUG_ON(in_interrupt()) and crashing the kernel.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This is a hardware-specific local DoS with no demonstrated memory corruption, no network reachability, and no plausible privilege-escalation primitive supported by the patch.

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

Patch: drm/amd/display: Wrap DCN32 phantom-plane allocation in DC_RUN_WITH_PREEMPTION_ENABLED
Commit: 30bb2ec6695d62f63db4aa6179c4626834ed0cd6
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=30bb2ec6695d62f63db4aa6179c4626834ed0cd6

Commit description:

[Why]
dcn32_validate_bandwidth() wraps dcn32_internal_validate_bw() with
DC_FP_START()/DC_FP_END(). In x86 non-RT, DC_FP_START takes fpregs_lock(),
which disables local softirqs.

The DML1 path through dcn32_enable_phantom_plane() calls kvzalloc() to
allocate ~335 KiB for dc_plane_state. This triggers the vmalloc path,
which calls BUG_ON(in_interrupt()) because it's invoked within the
FPU-enabled (softirq disabled) region, leading to a kernel crash.

[How]
Wrap the dc_state_create_phantom_plane() call with the
DC_RUN_WITH_PREEMPTION_ENABLED() macro to allow preemption during
this memory allocation.

Fixes: 235c676 ("drm/amd/display: add DCN32/321 specific files for Display Core")
Closes: https://gitlab.freedesktop.org/drm/amd/-/work_items/4470
Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Signed-off-by: James Lin <pinglei.lin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 885ccbe )
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.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=30bb2ec6695d62f63db4aa6179c4626834ed0cd6

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

The original Linux kernel CVE announcement for CVE-2026-53285 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53285

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: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: 1
  Paranoid ActionableScore: 2

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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).