[CVE-2026-72388][MODERATE REGULAR] drm/panthor: Always use the IRQ-safe variant when acquiring the fence lock [ Upstream

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

CVE: CVE-2026-72388
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: drm/panthor: Always use the IRQ-safe variant when acquiring the fence lock [ Upstream
Commit: 2946aa6c97ac0e0d777baef8c0e6d944da8724a3
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2946aa6c97ac0e0d777baef8c0e6d944da8724a3
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72388
Analysis date: Sun, 16 Aug 2026 05:15:25 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Borderline Moderate. Manual review recommended
Manual review required: YES

Summary:
`drm panthor used a non IRQ safe spin_lock for a dma_fence related lock that may be accessed from hardirq context, allowing a local GPU user to trigger an IRQ lock inversion or deadlock and cause denial of service.`

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

The original Linux kernel CVE announcement for CVE-2026-72388 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72388

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
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CVE-2026-72388	MODERATE	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	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-667;CWE-362;*CWE-833;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'drm panthor used a plain spin_lock when protecting the queue fence_ctx lock around dma_fence state and in_flight_jobs lists. Since dma_fence objects can be shared with other subsystems and accessed from hardirq context, an interrupt may try to take the same lock while normal context already holds it, causing an IRQ related lock inversion or deadlock. A local user that can submit GPU work or use a DRM render node may be able to reach this path through fence creation, signalling, timeout, or fault handling. For the CVSS the PR:L is used because local user context is required, but full administrative privileges are not necessarily required on systems where render nodes are exposed to unprivileged users. The issue is not network reachable. Impact is denial of service through GPU driver or kernel lockup, with no concrete evidence of information disclosure or privilege escalation from this patch.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline Moderate. Manual review recommended (with actual score 3)  SKIP CVE-2026-72388 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	LOCK RACE TIMER HARDWARE MEMORY  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH	-	-	checked

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

ActionableScore=3
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: **2**
* Paranoid score: **3**
* Final recommended bucket: **Borderline Moderate. Manual review recommended**::

## 2. Signal breakdown

Conservative signals:

* **Local unprivileged trigger: +1**
  A local user may be able to reach panthor DRM scheduling paths through GPU job submission or DRM render node access on systems exposing the device to unprivileged users.

* **Reliable kernel crash / strong DoS: +1**
  The bug is an IRQ locking mismatch. A plain `spin_lock()` is used for a `dma_fence` related lock that may also be taken from hardirq context, which can cause lock inversion or deadlock.

* **Hard or unreliable race / special timing required: -1**
  Triggering requires the affected lock to be held while a hardirq-context fence access occurs. This is timing dependent.

* **Availability impact realistic: +1**
  Deadlock in a GPU scheduler or fence signalling path can cause a kernel lockup or severe device/system availability impact.

Paranoid difference:

* In the paranoid interpretation, the hard timing penalty is not applied because fence signalling from IRQ context may be naturally reachable under real GPU workloads on affected hardware.

No memory corruption, UAF, OOB write, arbitrary write, info leak, or LPE primitive is supported by the patch.

## 3. Reachability analysis

The issue is local, not network reachable. The likely trigger is a local process submitting GPU work or interacting with the panthor DRM driver so that `dma_fence` objects are created, signalled, timed out, or fault processed while another subsystem accesses the same fence from hardirq context.

Privileges depend on device node policy. On many desktop or accelerator deployments, DRM render nodes can be available to unprivileged local users, so PR:L is reasonable. If the panthor device node is restricted to root or a trusted GPU service, practical reachability is lower.

The path is hardware and driver specific. It affects systems using the panthor DRM driver, not a broad default kernel path.

## 4. Severity interpretation

This behaves like an actionable Moderate / borderline manual-review issue, not an Important-class vulnerability. The realistic impact is denial of service through deadlock or kernel/GPU lockup. The patch does not show memory lifetime corruption, attacker-controlled object reuse, overwrite, type confusion, or a privilege escalation path.

Theoretical concern comes from DRM fence sharing and IRQ context interaction, but the demonstrated primitive is locking misuse, not memory corruption.

## 5. One-sentence report phrase

`drm panthor used a non IRQ safe spin_lock for a dma_fence related lock that may be accessed from hardirq context, allowing a local GPU user to trigger an IRQ lock inversion or deadlock and cause denial of service.`

## 6. Manual review recommendation

**MANUAL CHECK RECOMMENDED**

Reason: this is not memory corruption and does not justify Important by itself, but DRM render node exposure plus `dma_fence` hardirq locking makes the DoS plausibly reachable on affected hardware.

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

Patch: drm/panthor: Always use the IRQ-safe variant when acquiring the fence lock [ Upstream
Commit: 2946aa6c97ac0e0d777baef8c0e6d944da8724a3
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2946aa6c97ac0e0d777baef8c0e6d944da8724a3

Changed files:
  drivers/gpu/drm/panthor/panthor_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=2946aa6c97ac0e0d777baef8c0e6d944da8724a3

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

The original Linux kernel CVE announcement for CVE-2026-72388 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72388

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:N/I:N/A:H
  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: 2
  Paranoid ActionableScore: 3

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).