[CVE-2026-53140][LOW] drm/v3d: Fix vaddr leak when indirect CSD has zeroed workgroups

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

CVE: CVE-2026-53140
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: drm/v3d: Fix vaddr leak when indirect CSD has zeroed workgroups
Commit: 0b59d0946913a0df7d1a033013e259e9b6a76546
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0b59d0946913a0df7d1a033013e259e9b6a76546
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53140
Analysis date: Fri, 26 Jun 2026 03:51:16 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A local user with access to the V3D DRM render interface can submit an indirect CSD job with zero workgroup counts and leak BO vaddr mappings, potentially causing resource exhaustion and denial of service.

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

The original Linux kernel CVE announcement for CVE-2026-53140 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53140

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-53140	LOW	CHECK	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-401;*CWE-772;**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 resource leak in the V3D DRM scheduler can occur when v3d_rewrite_csd_job_wg_counts_from_indirect() handles an indirect CSD job whose workgroup count contains zero. The function maps both the indirect BO and the workgroup BO, but the old early return skipped the matching v3d_put_bo_vaddr() cleanup calls and leaked vaddr mappings. For the CVSS the PR:L is used because a local process with access to the V3D DRM render interface can submit GPU jobs, while full administrator privileges are not normally required for render node access. The issue is not network reachable and requires local code execution on a system with the V3D driver and accessible DRM device nodes. Impact is denial of service through resource exhaustion after repeated triggering. No confidentiality or integrity impact is assigned because the primitive is a mapping reference leak rather than UAF, OOB access, or arbitrary write.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)  SKIP CVE-2026-53140  SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	READ SIMPLEFIX LEAK HARDWARE LINUS  INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**

## 2. Signal breakdown

* Local unprivileged trigger: +1
  A local process with access to the V3D DRM render node can likely submit the affected indirect CSD job. Full root privileges are not normally required for DRM render node access.

* Availability impact realistic: +1
  The skipped `v3d_put_bo_vaddr()` calls leak BO vaddr mappings. Repeated triggering could cause resource exhaustion and local DoS.

* No generic memory corruption: +0
  The patch shows a cleanup-path bug causing leaked mappings. There is no UAF, double-free, OOB write, arbitrary write, or object confusion primitive.

* No confidentiality or integrity primitive: +0
  The leaked mapping references do not provide a demonstrated read-back path, data corruption path, or privilege escalation primitive.

* No remote reachability: +0
  The affected path is local DRM job submission, not network packet processing or remotely reachable protocol parsing.

* No admin/root penalty: +0
  Although the affected system must expose V3D DRM nodes, the realistic trigger can be a local user with render-node access, so `Requires admin/root` is not applied.

## 3. Reachability analysis

The bug is reachable by a local process able to submit V3D DRM jobs using the indirect CSD CPU job extension. This is typically possible through DRM render nodes on systems using the V3D driver, depending on device-node permissions and local graphics stack configuration. Containers or sandboxes may matter if `/dev/dri/renderD*` is passed through, but the issue does not inherently cross a namespace boundary by itself. The path is not default-exposed on all Linux systems because it depends on V3D hardware and driver availability, but on affected devices it is reachable through an ordinary local device interface.

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like local resource leak. The realistic impact is local denial of service through gradual resource exhaustion after repeated triggering. The patch does not support a memory corruption, privilege escalation, information disclosure, or shared-page ownership bypass interpretation. Theoretical impact beyond DoS is not well supported by the code change.

## 5. One-sentence report phrase

A local user with access to the V3D DRM render interface can submit an indirect CSD job with zero workgroup counts and leak BO vaddr mappings, potentially causing resource exhaustion and denial of service.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This is a straightforward resource leak fix with no visible memory corruption or security-boundary bypass primitive.

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

Patch: drm/v3d: Fix vaddr leak when indirect CSD has zeroed workgroups
Commit: 0b59d0946913a0df7d1a033013e259e9b6a76546
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0b59d0946913a0df7d1a033013e259e9b6a76546

Commit description:

v3d_rewrite_csd_job_wg_counts_from_indirect() maps both the indirect
buffer and the workgroup buffer and is expected to release them before
returning. When any of the workgroup counts read from the buffer is zero,
the function bailed out early and skipped the cleanup, leaking the vaddr
mappings of both BOs.

Jump to the cleanup path instead of returning directly, so the mappings
are always dropped.

Cc: stable@vger.kernel.org
Fixes: 18b8413 ("drm/v3d: Create a CPU job extension for a indirect CSD job")
Suggested-by: Jose Maria Casanova Crespo <jmcasanova@igalia.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Link: https://patch.msgid.link/20260602-v3d-fix-indirect-csd-v4-1-654309e32bc0@igalia.com
Signed-off-by: Maíra Canal <mcanal@igalia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/v3d/v3d_sched.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=0b59d0946913a0df7d1a033013e259e9b6a76546

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

The original Linux kernel CVE announcement for CVE-2026-53140 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53140

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).