[CVE-2026-98782][LOW] drm/mediatek: Fix ovl adaptor platform device leak

[CVE-2026-98782][LOW] drm/mediatek: Fix ovl adaptor platform device leak

[AL-KERNEL]

CVE: CVE-2026-98782
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: drm/mediatek: Fix ovl adaptor platform device leak
Commit: 3d85bd738aba61df14dfaf8fe638e2172d8427bf
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3d85bd738aba61df14dfaf8fe638e2172d8427bf
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98782
Analysis date: Fri, 23 Oct 2026 19:41:44 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
A missing platform device unregister operation leaks the Mediatek OVL adaptor after probe failure or driver removal, but reliable attacker driven repetition requires host administrative device management and no memory corruption or security boundary impact is established.

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

The original Linux kernel CVE announcement for CVE-2026-98782 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98782

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-2026-98782	LOW	https://www.kernelcve.org/list/?q=CVE-2026-98782 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT LOW AEGIS_AS=0 LEGACY=LOW RESULT=SAME (final reconciliation agrees; DECISION: both LOW)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';*CWE-772;CWE-404;*CWE-401;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.4';DESCR 'The Mediatek DRM probe path can leave a registered OVL adaptor platform device behind when a later initialization step fails. The normal driver removal path can retain the same child device after the parent DRM driver is unbound. A single occurrence is expected to cause persistent resource retention rather than immediate system failure, while repeated bind, unbind, or failed probe cycles could accumulate leaked platform devices and eventually interfere with driver initialization or exhaust kernel resources. For the CVSS the PR:H value is used because reliable triggering normally requires host administrator access to control platform driver binding or to reproduce the relevant probe failure. The issue is local and is not directly network reachable. The demonstrated impact is availability degradation only, with no supported UAF, OOB access, information disclosure, arbitrary write, or privilege escalation primitive. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 4.4 and the production ActionableScore returned 0 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. No severity changing production threshold or specialist override was recorded. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. The independent weaker Aegis shadow evaluated CVSS 0.0 and ActionableScore 0 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was LOW. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0)	MAYBE	INIT SIMPLEFIX LEAK ERRORPATH HARDWARE LINUS 	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=0
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=YES
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=YES
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw conservative score: -1
* Conservative score: 0
* Raw paranoid score: -1
* Paranoid score: 0
* Applied score range minimum: -1 -> 0
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +1 Concrete persistent kernel resource leak. The registered OVL adaptor platform device is not unregistered after probe failure or normal driver removal.
* -2 Proven host-administrator requirement for an attacker-driven trigger. Reliably forcing platform-driver probe, removal, bind, or unbind requires control of host platform-device management.
* No resource-exhaustion bonus. The patch proves retention of one platform device per affected lifecycle, but does not establish practical host-wide exhaustion or inexpensive below-admin accumulation.
* No crash bonus. Neither a kernel crash nor a device or host failure is demonstrated.
* No UAF, OOB access, double release, active-state corruption, shared-backing write, authorization bypass, or security-boundary crossing is established.
* NEW52 B5-R does not apply because there is no heap OOB write, retry-accumulated index, or later consumption of corrupted state.
* NEW53 B3-PENDING does not apply because no shared or file-backed storage is modified.
* V33 and V34 do not apply because no attacker-influenced active structured state is corrupted.
* NEW54 B4-PENDING does not apply because no DENY-to-ALLOW authorization decision changes.

3. Reachability analysis

The affected path is specific to Mediatek display pipelines that instantiate the OVL adaptor. An ordinary logged-in user, DRM client, compositor, or DRM master does not normally control platform-driver probe failure or driver unbinding through this path. Reliable repetition requires host-level platform-driver management, normally through privileged bind, unbind, module, or device-management operations.

The platform device is host-owned and is not scoped to an attacker-created user or network namespace. No delegated KMS interface shown in the patch reaches the missing unregister operation. Special Mediatek display hardware is required, but no separate hardware rarity penalty is applied merely because this is a device driver. There is no race.

4. Primitive and severity interpretation

The exact defect is a missing `platform_device_unregister()` after a successful `platform_device_register_data()`. It creates a persistent resource and reference leak during probe unwind and normal removal.

This is not a stale post-lifetime use. The device remains registered rather than being freed and subsequently accessed. There is no repeated release, refcount mutation through freed storage, or active structured-object corruption. PrimitiveClass is therefore NONE and RealUAF is NO.

The demonstrated consequence is retained kernel device state. Repeated privileged lifecycle operations might accumulate devices or interfere with reprobe, but host-wide resource exhaustion is unresolved. There is no supported confidentiality, integrity, privilege-escalation, or cross-boundary consequence. ImportantCandidate is NO and automatic downgrade is allowed.

5. One-sentence report phrase

A missing platform device unregister operation leaks the Mediatek OVL adaptor after probe failure or driver removal, but reliable attacker driven repetition requires host administrative device management and no memory corruption or security boundary impact is established.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

The patch establishes only a host-admin-triggered platform-device resource leak without OOB access, UAF, authorization bypass, crash, or credible cross-boundary primitive.

7. Call-site confidence

Call-site confidence: high

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

Patch: drm/mediatek: Fix ovl adaptor platform device leak
Commit: 3d85bd738aba61df14dfaf8fe638e2172d8427bf
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3d85bd738aba61df14dfaf8fe638e2172d8427bf

Commit description:

mtk_drm_probe() creates an OVL adaptor platform device with
platform_device_register_data() when the display pipeline requires the
OVL adaptor.

If a later initialization step fails, the probe error path releases
the DRM resources without unregistering the already registered OVL
adaptor device. The normal remove path likewise leaves the device
registered after the DRM driver is unbound.

Keep track of whether the OVL adaptor was successfully registered and
unregister it on probe failure. Also recover the platform device from
the stored DDP component device and unregister it during normal
removal.

The issue was identified by a static analysis tool I developed and
confirmed by manual review.

Fixes: 0d9eee9 ("drm/mediatek: Add drm ovl_adaptor sub driver for MT8195")
Cc: stable@vger.kernel.org
Signed-off-by: Guangshuo Li <lgs201920130244@gmail.com>
Link: https://patchwork.kernel.org/project/linux-mediatek/patch/20260921131156.403652-1-lgs201920130244@gmail.com/
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/mediatek/mtk_drm_drv.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=3d85bd738aba61df14dfaf8fe638e2172d8427bf

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

The original Linux kernel CVE announcement for CVE-2026-98782 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98782

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:H/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.4

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: 0

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).