[CVE-2026-98783][MODERATE REGULAR] drm/mediatek: Add missing IS_ERR check for ovl_adaptor platform device

[CVE-2026-98783][MODERATE REGULAR] drm/mediatek: Add missing IS_ERR check for ovl_adaptor platform device

[AL-KERNEL]

CVE: CVE-2026-98783
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: drm/mediatek: Add missing IS_ERR check for ovl_adaptor platform device
Commit: 4acac370aad2d4895a82f40b2f03e9ef70eecaa6
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4acac370aad2d4895a82f40b2f03e9ef70eecaa6
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98783
Analysis date: Mon, 19 Oct 2026 01:13:23 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
An unchecked ERR_PTR returned during MediaTek OVL adaptor registration can propagate into DRM component initialization and cause a host kernel crash, but reliable triggering requires host driver management and no useful memory corruption or privilege escalation primitive is established.

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

The original Linux kernel CVE announcement for CVE-2026-98783 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98783

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
======================================================================

CVE-2026-98783	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98783 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=2 LEGACY=MODERATE RESULT=DIFF V39_AEGIS_ONE_STEP_UP=LOW->MODERATE TEMP_DISTANCE_MERGE_SKIP=AEGIS_NO_POSITIVE_SEVERITY_EVIDENCE (final Legacy and Aegis differ; FINAL: MODERATE, Aegis: MODERATE_KPANIC)	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-252;CWE-754;CWE-703;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.4';DESCR 'The MediaTek DRM probe path uses the return value of platform_device_register_data without checking whether it is an ERR_PTR. If registration fails, an invalid pointer derived from ovl_adaptor can be stored in ddp_comp and passed to later component initialization code, potentially causing a kernel oops or panic. For the CVSS the PR:H is selected because reliable triggering normally requires administrative control over driver loading, device binding, or repeated probe operations on supported MediaTek hardware. The issue is not network reachable and no unprivileged remote trigger is apparent. Impact is denial of service through a kernel crash. The analyzed path does not provide evidence of UAF, OOB access, information disclosure, arbitrary write, or privilege escalation. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. 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. Recorded rule transitions were CVSS and initial triage stage MODERATE_KPANIC to MODERATE because the CVSS score, vector or bug class threshold rule was applied. ActionableScore thresholds stage MODERATE to LOW because the ActionableScore threshold rule was applied. final reconciliation stage LOW to MODERATE because KP specialist did not establish a qualifying panic and the cross model evidence reconciliation rule was applied. 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. Exact triggered rule markers were DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS and DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 and KPANIC_UNSUPPORTED_REMOVED and V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 4.2 and ActionableScore 2 with primitive class CLASS_C and manual review RECOMMENDED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0)	MAYBE	DANGER SIMPLEFIX ERRORPATH HARDWARE LINUS DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 KPANIC_UNSUPPORTED_REMOVED V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED	-	-	checked

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

1. ActionableScore

* Raw conservative score: 0
* Conservative score: 0
* Raw paranoid score: 0
* Paranoid score: 0
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +1 Weak or indirect corruption candidate. `platform_device_register_data()` can return an `ERR_PTR`, from which an invalid `dev` pointer is stored in active driver state and passed to initialization helpers.
* +1 Realistic kernel crash. Subsequent consumption of the invalid pointer can cause an Oops or panic.
* -2 Host-administrator-equivalent trigger. Reliable attacker-controlled repetition of the probe path normally requires control over driver loading, binding, or reprobe of the host platform device.
* No UAF, OOB read or write, repeated release, refcount mutation, controlled reclaim, arbitrary write, disclosure, or authorization bypass is established.
* No additional availability point is awarded because it would double-count the same kernel crash.
* No attacker-controlled payload or useful target selection is demonstrated.
* B5-R does not apply because there is no heap OOB write, retry-accumulated offset, or later consumption of corrupted heap contents.
* B3-PENDING does not apply because no shared-backing write exists.
* B4-PENDING does not apply because `IS_ERR()` is an object-validity check, not an authorization guard.

3. Reachability analysis

The vulnerable operation occurs in `mtk_drm_probe()` while registering the MediaTek OVL adaptor platform device. An ordinary logged-in user, DRM client, compositor, DRM master, or delegated display service is not shown to control this probe-time allocation and registration path.

Reliable deliberate triggering normally requires host-level control over module loading, platform-driver binding, or repeated reprobe operations. Numeric host UID 0 is not proven to be mandatory because equivalent capabilities may suffice, so `RequiresHostUID0` remains unknown. The platform-device operation is not scoped to an attacker-created user or network namespace.

The affected path requires compatible MediaTek MT8195 display hardware and the OVL adaptor configuration. No separate rare-hardware penalty is applied merely because the code is a hardware driver. The failure can arise from allocation or registration failure, but ordinary memory pressure alone does not establish a reliable unprivileged trigger. No race is involved.

4. Primitive and severity interpretation

The exact primitive is propagation and later consumption of an `ERR_PTR`-derived invalid device pointer. This is active invalid state, but not a post-lifetime object, UAF, type confusion, or demonstrated memory overwrite. The invalid value is expected to cause a fault when downstream code treats it as a valid `struct device`.

This is `CLASS_C` because the supported consequence is invalid-state consumption and kernel crash without an independently useful corruption primitive. The demonstrated effect is denial of service. Privilege escalation, confidentiality loss, controlled integrity impact, and useful behavior beyond the crash are unsupported.

`ImportantCandidate=NO` because there is no Class A primitive, meaningful Class B lifetime violation, authorization bypass, or unresolved cross-boundary corruption chain. `AutoDowngradeAllowed=YES` because automatic handling would not discard a concrete exploitation primitive requiring Important-versus-Moderate review.

5. One-sentence report phrase

An unchecked ERR_PTR returned during MediaTek OVL adaptor registration can propagate into DRM component initialization and cause a host kernel crash, but reliable triggering requires host driver management and no useful memory corruption or privilege escalation primitive is established.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

The issue is a hardware-specific, host-administrator-triggered invalid-pointer crash with no UAF, OOB write, authorization bypass, or unresolved security-boundary primitive.

7. Call-site confidence

Call-site confidence: medium

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

Patch: drm/mediatek: Add missing IS_ERR check for ovl_adaptor platform device
Commit: 4acac370aad2d4895a82f40b2f03e9ef70eecaa6
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4acac370aad2d4895a82f40b2f03e9ef70eecaa6

Commit description:

platform_device_register_data() can fail and return an ERR_PTR, but the
return value is used without checking, leading to an invalid pointer
being stored in ddp_comp[].dev and passed to component_match_add() and
mtk_ddp_comp_init(), which could result in a kernel crash.

Add an IS_ERR() check to jump to the error handling path on failure.

Fixes: 0d9eee9 ("drm/mediatek: Add drm ovl_adaptor sub driver for MT8195")
Cc: stable@vger.kernel.org
Signed-off-by: Haojie Li <lihaojie@kylinos.cn>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Link: https://patchwork.kernel.org/project/linux-mediatek/patch/20260825100845.438893-1-lihaojie@kylinos.cn/
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=4acac370aad2d4895a82f40b2f03e9ef70eecaa6

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

The original Linux kernel CVE announcement for CVE-2026-98783 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98783

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:H/UI:N/S:U/C:N/I:N/A:H
  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: 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).