[CVE-2026-53376][MODERATE REGULAR] drm/amdkfd: Add upper bound check for num_of_nodes

[CVE-2026-53376][MODERATE REGULAR] drm/amdkfd: Add upper bound check for num_of_nodes

[AL-KERNEL]

CVE: CVE-2026-53376
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: drm/amdkfd: Add upper bound check for num_of_nodes
Commit: 4a8093c7def141cc6e854fbe3f9693867982418f
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4a8093c7def141cc6e854fbe3f9693867982418f
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53376
Analysis date: Sun, 19 Jul 2026 06:43:53 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline, manual review recommended. Not Actionable Moderate at minimum
Manual review required: YES

Summary:
A missing upper bound check in the AMD KFD process aperture ioctl allowed a local caller with `/dev/kfd` access to provide a `num_of_nodes` value larger than the real topology device count, potentially causing incorrect driver behavior or denial of service, but no concrete memory corruption or privilege escalation primitive is shown by the patch.

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

The original Linux kernel CVE announcement for CVE-2026-53376 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53376

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: 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-2026-53376	MODERATE	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-20;CWE-129;**CWE-400;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'A missing upper bound check in the AMD KFD process aperture ioctl allowed a local caller to pass a num_of_nodes value larger than the actual number of KFD topology devices. The affected path is kfd_ioctl_get_process_apertures_new() and the input is processed while filling process aperture information for GPU nodes. For the CVSS the PR:L is used because reliable triggering requires local access to the KFD device interface such as /dev/kfd, usually granted to users or services with GPU compute access rather than to a remote network attacker. The issue is not network reachable and is triggered through a local device ioctl. Impact is primarily denial of service or incorrect ioctl behavior. There is no strong evidence in the provided diff for a UAF, OOB write, information leak, or privilege escalation primitive, so confidentiality and integrity are kept at N for both base and paranoid scoring.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended. Not Actionable Moderate at minimum (with actual score 4)  SKIP CVE-2026-53376 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	SIMPLEFIX LOG HARDWARE  INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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

ActionableScore=4
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 4
* Final recommended bucket: **Borderline, manual review recommended. Not Actionable Moderate at minimum**

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1
  The affected path is a local `/dev/kfd` ioctl. It may be reachable by users with GPU compute access, commonly via render/video-style device permissions.

* Weak or indirect corruption candidate: +1
  `num_of_nodes` is user supplied and was not checked against the real KFD topology device count. This is an unchecked object-count or object-index style validation bug, but the patch does not show UAF, OOB write, arbitrary write, type confusion, or attacker-controlled reclaim.

* Availability impact plausible: +1
  A too-large node count could plausibly cause incorrect ioctl behavior, excessive iteration, or driver-side failure. The evidence supports DoS-style impact more than confidentiality or integrity impact.

Paranoid additional signal:

* Driver-local state or DoS concern: +1
  Because this is a GPU kernel driver ioctl operating on topology objects, manual review should confirm whether oversized `num_of_nodes` can reach any copy, enumeration, or array-index path not visible in the provided snippet.

Signals not applied:

* No Generic memory corruption +2
  The patch is an upper-bound validation fix and does not demonstrate UAF, OOB write, double-free, refcount misuse, or type confusion.

* No Privilege escalation plausible +2
  No reclaim, overwrite, callback, object replacement, or credential/security-boundary primitive is shown.

* No Remote reachable +2
  This is a local device ioctl, not a network path.

* No high-control GPU API bonus
  The patch does not show attacker control over memory layout, object lifetime, callbacks, refcounts, DMA mappings, or page ownership.

## 3. Reachability analysis

The likely trigger is a local process that can open the AMD KFD device and issue `kfd_ioctl_get_process_apertures_new()`. This usually means a user or service with access to `/dev/kfd` and AMD GPU compute functionality.

Namespaces or containers can matter if `/dev/kfd` is passed into a container or exposed to reduced-privilege workloads. In that case the practical privilege requirement remains closer to PR:L than PR:H, because the attacker does not need full host root if the device node is delegated.

The path is not network reachable. It depends on AMD KFD being present and accessible, but this is still an ordinary local device interface on affected GPU systems, not an obscure debug-only path.

Call-site confidence: medium. The changed ioctl path is visible, but the full loop and copy/enumeration logic after the check is not fully included in the provided patch text.

## 4. Severity interpretation

This behaves more like a borderline local Moderate issue than an Important-class vulnerability. The realistic evidence points to input-validation failure with possible DoS or incorrect ioctl behavior.

Theoretical risk exists because a user-controlled node count is used in a kernel GPU driver path, and GPU drivers are complex. However, the patch does not show a concrete memory corruption primitive, information leak, privilege escalation path, stale pointer, or attacker-controlled overwrite. Therefore the conservative score should stay below Actionable Moderate.

## 5. One-sentence report phrase

A missing upper bound check in the AMD KFD process aperture ioctl allowed a local caller with `/dev/kfd` access to provide a `num_of_nodes` value larger than the real topology device count, potentially causing incorrect driver behavior or denial of service, but no concrete memory corruption or privilege escalation primitive is shown by the patch.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: this is a user-controlled kernel ioctl parameter in a GPU driver, so the surrounding enumeration and copy paths should be checked manually. It is not strong enough for MANUAL CHECK REQUIRED because the provided patch only shows validation of an oversized count and does not demonstrate UAF, OOB write, information disclosure, or LPE.

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

Patch: drm/amdkfd: Add upper bound check for num_of_nodes
Commit: 4a8093c7def141cc6e854fbe3f9693867982418f
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4a8093c7def141cc6e854fbe3f9693867982418f

Commit description:

drm/amdkfd: Add upper bound check for num_of_nodes
in kfd_ioctl_get_process_apertures_new.

Reviewed-by: Harish Kasiviswanathan <Harish.Kasiviswanathan@amd.com>
Signed-off-by: Alysa Liu <Alysa.Liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 98ff46a )
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
  drivers/gpu/drm/amd/amdkfd/kfd_priv.h
  drivers/gpu/drm/amd/amdkfd/kfd_topology.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=4a8093c7def141cc6e854fbe3f9693867982418f

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

The original Linux kernel CVE announcement for CVE-2026-53376 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53376

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: 3
  Paranoid ActionableScore: 4

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).