[CVE-2026-99119][MODERATE 7.0] drm/amdgpu/userq: actually validate userq BOs [ Upstream

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

CVE: CVE-2026-99119
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: drm/amdgpu/userq: actually validate userq BOs [ Upstream
Commit: d1d6b859e89dd274cd0fae77503cdf91be8310c0
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d1d6b859e89dd274cd0fae77503cdf91be8310c0
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99119
Analysis date: Wed, 28 Oct 2026 23:09:51 -0400
ActionableScore: 5
ActionableScore lower bound: unknown
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
A low-privilege AMDGPU userq operation can race BO teardown and pass a freed active GEM/TTM object to DRM execution preparation, creating a kernel UAF with plausible denial of service and unresolved corruption leverage.

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

The original Linux kernel CVE announcement for CVE-2026-99119 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99119

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 7.0
Manual review required: YES

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-2026-99119	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-99119 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=0 LEGACY=MODERATE_KPANIC RESULT=SAME (final reconciliation agrees; DECISION: both MODERATE_KPANIC)	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-362;*CWE-672;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'amdgpu_userq_bo_validate iterated always_valid.evicted instead of individual.evicted, so BOs created and evicted before userq creation could be skipped and fail to receive eviction fence rearm. The same path obtained a BO pointer under individual_lock but released the lock before drm_exec_prepare_obj acquired its own object reference, leaving a race window where concurrent BO or VM teardown could free the object and cause a use after free dereference. For the CVSS the PR:L value reflects that a local process generally needs access to an AMDGPU render node and the userq interfaces. Triggering the lifetime failure requires race timing and affected GPU support, and there is no direct network path. Impact is at least GPU or kernel denial of service and the concrete missing lifetime reference makes memory corruption impact plausible, while an arbitrary write or reliable privilege escalation primitive is not proven. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 7 and the production ActionableScore returned 5 with recommendation Actionable Moderate / Strong Important candidate requiring manual review. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage LOW to MODERATE_KPANIC because the ActionableScore threshold rule was applied. The legacy KP specialist produced a review artifact and its decision was processed by the applicable KP rules. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were INCREASED_TO_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4. The independent weaker Aegis shadow evaluated CVSS 0.0 and ActionableScore 0 with primitive class NONE and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5)	MAYBE	SIMPLEFIX LEAK HARDWARE  KPANIC INCREASED_TO_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4	-	-	checked

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

ActionableScore=5
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=NO
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 4.
* Conservative score: 5. REAL UAF FLOOR 5 applies because a below-host-admin render-node/userq interface reaches non-cleanup processing of an active structured BO.
* Raw paranoid score: 4.
* Paranoid score: 5; no additional speculative leverage added.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

* +2 — Real UAF/lifetime violation: `bo` is obtained under `individual_lock`, the lock is dropped, and the vulnerable code calls `drm_exec_prepare_obj()` without first holding a BO reference. Concurrent teardown can free it.
* +1 — Local below-host-admin trigger: supplied evidence grounds access through AMDGPU render-node/userq interfaces with low privileges.
* +1 — Plausible kernel/GPU crash: dereferencing or locking/refcounting the freed GEM/TTM object can fault.
* +0 — Wrong-list iteration separately skips validation and eviction-fence rearming, but no independently quantified corruption consequence is shown.
* No race penalty: a race is required, but the evidence does not establish a narrow, one-shot, or externally uncontrollable window.
* No controlled reclaim, attacker-shaped replacement, arbitrary write, disclosure, or proven LPE.
* No extra Availability point for the same crash.
* NEW52 B5-R does not apply: no retry-accumulated heap OOB write is shown.
* B4-PENDING does not apply: no authorization decision or omitted security guard exists.

3. Reachability analysis

A local process with access to the affected AMDGPU render node and userq interface can create/use BOs and exercise validation; host UID 0 or host-administrator capability is not indicated. The complete operation is not shown to be namespace-scoped. A supported AMD GPU and userq functionality are prerequisites, but this is not evidence of rare physical-only hardware. Concurrent BO/VM teardown supplies the race, although exact repeatability is not shown.

4. Primitive and severity reading

This is an active structured-object UAF, not fixed stale storage or cleanup-only dereference. The stale `amdgpu_bo`/GEM object is passed into `drm_exec_prepare_obj()`, which performs active reservation/reference preparation. The added temporary reference closes the lifetime window. There is no concrete repeated-release sequence and no proof of controlled reuse, so this remains CLASS_B rather than CLASS_A.

ImportantCandidate is YES because a low-privilege GPU interface can race lifetime termination of an active kernel object that is subsequently consumed by privileged DRM/TTM code; exploit leverage beyond crash remains unresolved. Auto-downgrade is therefore unsafe.

5. One-sentence report phrase

A low-privilege AMDGPU userq operation can race BO teardown and pass a freed active GEM/TTM object to DRM execution preparation, creating a kernel UAF with plausible denial of service and unresolved corruption leverage.

6. Manual review advice

MANUAL CHECK REQUIRED

Review reclaim feasibility, the fields and refcount/locking operations consumed by `drm_exec_prepare_obj()`, and practical render-node race repeatability.

7. Call-site confidence

Call-site confidence: medium

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

Patch: drm/amdgpu/userq: actually validate userq BOs [ Upstream
Commit: d1d6b859e89dd274cd0fae77503cdf91be8310c0
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d1d6b859e89dd274cd0fae77503cdf91be8310c0

Changed files:
  drivers/gpu/drm/amd/amdgpu/amdgpu_userq.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=d1d6b859e89dd274cd0fae77503cdf91be8310c0

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

The original Linux kernel CVE announcement for CVE-2026-99119 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99119

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:L/I:L/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: 5

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: YES
Published priority for this report (same as in Subject): MODERATE 7.0

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).