[CVE-2026-31540][LOW] drm/i915/gt: Check set_default_submission() before deferencing [ Upstream

[CVE-2026-31540][LOW] drm/i915/gt: Check set_default_submission() before deferencing [ Upstream

[AL-KERNEL]

CVE: CVE-2026-31540
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: drm/i915/gt: Check set_default_submission() before deferencing [ Upstream
Commit: db8b1bebe81ffb410ddd746b6869f72e22420850
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=db8b1bebe81ffb410ddd746b6869f72e22420850
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-31540
Analysis date: Sun, 02 Aug 2026 07:40:23 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-31540 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-31540

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-2026-31540	LOW	CHECK WITH IMPACT FROM ORIG NN MODERATE	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-476;CWE-703;CWE-754;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'A NULL function pointer dereference in the i915 GT suspend path can occur when i915 firmware binaries are missing and engine set_default_submission is not initialized. During suspend, intel_engines_reset_default_submission calls this callback and may jump to address 0, causing a kernel oops or panic. For the CVSS the PR:L is used in the paranoid score because a local user may be able to request suspend through power management policy on some desktop systems, although server deployments may restrict this to administrators. The issue is not network reachable and does not provide an evident memory corruption primitive beyond a NULL function pointer call. Impact is denial of service through kernel crash or failed suspend only.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)  SKIP CVE-2026-31540  SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	DANGER NULLPTR HARDWARE  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	-	-	checked

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

ActionableScore=2

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

2. Signal breakdown
* Reliable kernel crash / strong DoS: +1. The trace shows a kernel NULL function pointer dereference at RIP 0x0 during suspend.
* Local unprivileged trigger: +1. On many desktop or laptop systems, a local user may be allowed to request suspend through power management policy.
* Broad/common subsystem: +1. i915 is common on Intel client systems.
* Rare or configuration-dependent condition: -1. The crash requires the i915 firmware binaries to be missing so that set_default_submission is not initialized.
* No memory corruption bonus. This is a direct NULL callback invocation, not UAF, OOB write, double free, object reuse, or controlled function pointer corruption.
* No LPE bonus. The patch and call path do not show attacker control over the callback pointer or a realistic privilege escalation primitive.
* No confidentiality or integrity impact. The demonstrated effect is crash or failed suspend only.

3. Reachability analysis
A local actor may trigger the vulnerable path by initiating system suspend, depending on desktop policy, logind configuration, or administrative power controls. In server deployments this may effectively require administrator privileges. Namespaces and containers normally do not help because suspend is a host power-management operation, not a namespaced interface. The affected hardware class is common, but the required missing-firmware state is not a normal healthy deployment condition.

4. Severity interpretation
This behaves like an ordinary Moderate or Low-like local DoS. The theoretical dangerous-looking element is a kernel function pointer call, but the pointer is NULL rather than attacker-controlled, and the patch only adds a presence check before calling it. There is no evidence of memory lifetime corruption, reclaim, overwrite, type confusion, or privilege escalation.

5. One-sentence report phrase
A missing NULL check in the i915 GT suspend path can cause a kernel crash when firmware is absent and set_default_submission is not initialized, but the realistic impact is local denial of service only.

6. Manual review recommendation
NO MANUAL CHECK NEEDED. This is a configuration-dependent local NULL dereference during suspend with no supported memory-corruption or privilege-escalation primitive.

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

Patch: drm/i915/gt: Check set_default_submission() before deferencing [ Upstream
Commit: db8b1bebe81ffb410ddd746b6869f72e22420850
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=db8b1bebe81ffb410ddd746b6869f72e22420850

Changed files:
  drivers/gpu/drm/i915/gt/intel_engine_cs.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=db8b1bebe81ffb410ddd746b6869f72e22420850

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

The original Linux kernel CVE announcement for CVE-2026-31540 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-31540

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: 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).