[CVE-2026-93823][LOW] drm/amdkfd: Let driver decide buffer size at AMDKFD_IOC_GET_DMABUF_INFO ioctl [ Upstream

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

CVE: CVE-2026-93823
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: drm/amdkfd: Let driver decide buffer size at AMDKFD_IOC_GET_DMABUF_INFO ioctl [ Upstream
Commit: a65ccabde6deb95baf9442bd98299e2248884162
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a65ccabde6deb95baf9442bd98299e2248884162
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93823
Analysis date: Thu, 24 Sep 2026 17:50:51 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-93823 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93823

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.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-93823	LOW	https://www.kernelcve.org/list/?q=CVE-2026-93823 CHECK WITH IMPACT FROM ORIG NN LOW	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-789;**CWE-400;CWE-770;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'AMDKFD_IOC_GET_DMABUF_INFO accepted a user controlled metadata_size and passed it directly to kzalloc before determining the actual metadata size of the buffer object. A local render group user could request an extremely large allocation such as 2 GiB and repeat the ioctl to create memory pressure or potentially trigger OOM behavior in kernel context. For the CVSS the PR:L value is used because exploitation requires local code execution and access to the KFD device, but it normally does not require full administrative privileges. The issue is not network reachable. The demonstrated vulnerability class is resource exhaustion rather than memory corruption, so the base impact is limited availability loss. The paranoid assessment allows A:H when sustained requests can realistically cause severe memory exhaustion or a system wide OOM, while C:N and I:N remain unchanged because no UAF, out of bounds access, information leak, or write primitive is present.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)  SKIP CVE-2026-93823 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	NOMEMCHK HARDWARE MEMORY  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	-	-	checked

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

ActionableScore=2
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 2
* Conservative score: 2
* Raw paranoid score: 2
* Paranoid score: 2
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

Positive signals:

* +1 Local unprivileged trigger. The commit explicitly states that any render-group user with access to the KFD device can supply the hostile size.
* +1 Local unprivileged high-control kernel data-plane API. The caller directly controls the size passed to `kzalloc`, including requests around 2 GiB, and can repeat the ioctl.

Negative signals:

* No negative points applied. AMD GPU hardware is required, but common AMDGPU hardware is not sufficient evidence for a rare-hardware penalty.
* No host-admin penalty. Below-host-admin reachability is explicitly established for render-group users.

Material non-awarded signals:

* Reliable kernel crash or strong DoS was not awarded. The commit identifies potential OOM, but a large `kzalloc` request can simply fail with `ENOMEM`, and immediate host-wide failure is not established.
* Persistent resource leak was not awarded. The issue is an attacker-sized transient allocation, not a missing release or permanently lost reference.
* No UAF, OOB access, overwrite, disclosure, authorization bypass, or lifetime violation is established.
* Confidentiality and integrity signals were not awarded.
* Remote reachability is not established.
* Repetition can increase memory pressure, but it does not establish a separate corruption or isolation-bypass primitive.

3. Reachability analysis

The attacker is a local render-group user with access to `/dev/kfd` and a suitable DMA-BUF file descriptor. This is positively below host-admin privilege, so `HostAdminRequired=NO`.

The access boundary is a device-node permission or ACL rather than a namespace-scoped capability. No attacker-created user or network namespace is involved, so `NamespaceScopedPrivilege=NO`.

An AMD GPU with KFD enabled and exposed to the render group is required. This is prior system configuration, but it is normal for affected compute-capable AMDGPU deployments and does not justify a rare-hardware penalty. There is no race or timing requirement. The user can directly submit and repeat the ioctl.

4. Primitive and severity interpretation

The exact issue is an uncontrolled kernel memory allocation. Before the fix, `args->metadata_size` was supplied by userspace and passed directly to `kzalloc` before the driver determined the actual metadata size.

There is no stale object, UAF, repeated release, OOB access, or memory overwrite. Therefore this is neither active structured stale-object use nor fixed stale storage. It is a resource-exhaustion condition with no established corruption primitive, so `PrimitiveClass=NONE`.

The demonstrated practical consequence is allocation failure and possible memory pressure or OOM. Host-wide denial of service is plausible under sustained abuse but is not sufficiently established to receive a separate strong-DoS point. Privilege escalation, confidentiality impact, and integrity impact are unsupported.

`ImportantCandidate=NO` because no corruption, ownership, authorization, isolation, or persistent resource-leak primitive exists. `AutoDowngradeAllowed=YES` because the issue is limited to attacker-controlled transient allocation pressure and no unresolved Important-grade primitive remains.

Likely operational severity is Low to ordinary Moderate, depending on allocator behavior, available memory, and device-node exposure.

5. One-sentence report phrase

A local render-group user could supply an excessive metadata size to AMDKFD_IOC_GET_DMABUF_INFO and force a large kernel allocation attempt, potentially causing memory pressure or OOM without establishing memory corruption or privilege escalation.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

The patch establishes a straightforward local resource-exhaustion issue without UAF, overwrite, persistent leak, authorization bypass, or another primitive requiring Important-grade exploitation review.

7. Call-site confidence

Call-site confidence: high

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

Patch: drm/amdkfd: Let driver decide buffer size at AMDKFD_IOC_GET_DMABUF_INFO ioctl [ Upstream
Commit: a65ccabde6deb95baf9442bd98299e2248884162
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a65ccabde6deb95baf9442bd98299e2248884162

Changed files:
  drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.c
  drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h
  drivers/gpu/drm/amd/amdkfd/kfd_chardev.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=a65ccabde6deb95baf9442bd98299e2248884162

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

The original Linux kernel CVE announcement for CVE-2026-93823 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93823

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:L/UI:N/S:U/C:N/I:N/A:L
  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: unknown
  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).