[CVE-2026-98997][MODERATE 7.0] drm/amdgpu/userq: only accept doorbell BOs as queue doorbell

[CVE-2026-98997][MODERATE 7.0] drm/amdgpu/userq: only accept doorbell BOs as queue doorbell

[AL-KERNEL]

CVE: CVE-2026-98997
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: drm/amdgpu/userq: only accept doorbell BOs as queue doorbell
Commit: 112dbe2b10d6d088a6c599980dd960dcbfa55ff0
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=112dbe2b10d6d088a6c599980dd960dcbfa55ff0
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98997
Analysis date: Tue, 27 Oct 2026 02:42:28 -0400
ActionableScore: 5
ActionableScore lower bound: unknown
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
A render-node user can submit a shared regular GEM buffer as a queue doorbell, causing destructive domain migration that discards another client's shared buffer contents.

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

The original Linux kernel CVE announcement for CVE-2026-98997 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98997

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-2026-98997	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98997 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=3 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:L/PR:L/UI:N/S:U/C:N/I:L/A:L';*CWE-20;CWE-1287;CWE-284;BEST CVSS score: '4.4';DESCR 'A local AMDGPU user queue client could supply a regular or imported GEM buffer as doorbell_handle. Pinning that object into the doorbell domain can invoke ttm_bo_move_null and discard its contents, including contents belonging to another client that shared the buffer. This is a logic and input validation flaw with a concrete cross-client integrity impact and possible disruption of the affected GPU workload, but there is no evidence of UAF, OOB access, kernel memory corruption, information disclosure, privilege escalation, or a reliable host-wide crash. For the CVSS the PR:L value is used because exploitation requires a local user or process with access to the DRM render node, the user queue interface, and a valid shared GEM handle. The issue is not directly network reachable. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 4.4 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 manual review requirement 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_FROM_LOW_BASED_ON_REQUIREMANUALCHECK. The independent weaker Aegis shadow evaluated CVSS 4.4 and ActionableScore 3 with primitive class CLASS_C 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 HARDWARE  KPANIC INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK	-	-	checked

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

ActionableScore=5
PrimitiveClass=CLASS_A
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=CONFIRMED
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 5.
* Conservative score: 5; no floor or cap applied.
* Raw paranoid score: 5.
* Paranoid score: 5; no additional unsupported effects scored.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

* +2 Strong semantic reinterpretation: an ordinary or imported GEM BO is accepted as a queue doorbell resource and moved into the doorbell domain, where `ttm_bo_move_null()` discards its existing contents.
* +1 Local unprivileged trigger: supplied evidence grounds access through an AMDGPU render-node/user-queue client with a valid shared GEM handle, without host-administrator powers.
* +1 Integrity impact: the operation can destroy contents of the same GEM object shared by another client.
* +1 Practical chain: shared BO handle → submit as `doorbell_handle` → domain pin/move → contents discarded.
* No UAF, OOB write, arbitrary write, disclosure, LPE, reliable host crash, or protected-file/page-cache overwrite is shown.
* No additional cross-authority ownership/COW score: the clients reference the same shared GEM object, and distinct write permissions or a COW breach are not established.
* B4-PENDING does not apply: the new check validates BO type/domain, not an authorization decision changing DENY to ALLOW.

3. Reachability analysis

A local process needs AMDGPU render-node access, the user-queue interface, and a valid handle to a regular or imported shared BO. The supplied evidence supports a below-host-admin client trigger, so host UID 0 and effective host-administrator capability are not required. No namespace capability is involved or established. AMDGPU hardware and user-queue support are prerequisites, but the evidence does not justify a rare-hardware penalty. No race or retry sequence is required.

4. Primitive and severity reading

The primitive is active resource semantic reinterpretation: a normal data BO is treated as a doorbell BO, causing destructive migration and loss of another sharing client's buffer contents. This is CLASS_A semantic/resource corruption, not kernel-memory corruption or UAF. Cross-client integrity loss is shown; persistent storage corruption, host compromise, and privilege escalation remain unproven. Important candidacy follows from the concrete cross-client active-resource corruption, while mandatory review is needed to determine actual sharing permissions and victim impact.

5. One-sentence report phrase

A render-node user can submit a shared regular GEM buffer as a queue doorbell, causing destructive domain migration that discards another client's shared buffer contents.

6. Manual review advice

MANUAL CHECK REQUIRED

Confirm user-queue deployment exposure, dma-buf/GEM sharing permissions, and whether affected buffers can contain security-sensitive cross-client GPU state.

7. Call-site confidence

Call-site confidence: medium

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

Patch: drm/amdgpu/userq: only accept doorbell BOs as queue doorbell
Commit: 112dbe2b10d6d088a6c599980dd960dcbfa55ff0
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=112dbe2b10d6d088a6c599980dd960dcbfa55ff0

Commit description:

amdgpu_userq_get_doorbell_index() pins any BO passed as doorbell_handle
into the doorbell domain. For a regular BO, TTM moves it with
ttm_bo_move_null() and its contents are lost. Since an importer on the
same device gets the exporter's GEM object, a client can do this to a
buffer another client shared with it.

Reject BOs that were not created in the doorbell domain.

v2: drop the error message, use a local abo variable (Christian)

Fixes: f09c1e6 ("drm/amdgpu: generate doorbell index for userqueue")
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Jesse Zhang <Jesse.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit f7497bb )
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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=112dbe2b10d6d088a6c599980dd960dcbfa55ff0

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

The original Linux kernel CVE announcement for CVE-2026-98997 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98997

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: Not available
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L
  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: 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).