[CVE-2026-68251][LOW] drm/amdgpu/sdma6.0: replace BUG_ON() with WARN_ON()

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

CVE: CVE-2026-68251
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: drm/amdgpu/sdma6.0: replace BUG_ON() with WARN_ON()
Commit: 2eb06c88426b6c8de602c608959f3a56ac51861e
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2eb06c88426b6c8de602c608959f3a56ac51861e
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68251
Analysis date: Mon, 10 Aug 2026 14:24:23 -0400
ActionableScore: 1
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
An amdgpu SDMA fence alignment assertion used BUG_ON() and could crash the kernel if an internal fence address invariant was violated, but the value appears kernel-managed and the issue is not network reachable or supported by a memory corruption primitive.

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

The original Linux kernel CVE announcement for CVE-2026-68251 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68251

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
======================================================================

CVE-2026-68251	LOW	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-617;CWE-754;CWE-755;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'An assertion in sdma_v6_0_ring_emit_fence() used BUG_ON() when the SDMA fence address had the low two bits set. If that invariant is violated, the driver can crash the kernel instead of handling the condition as a warning, so the practical impact is local denial of service. For the CVSS the PR:L value is used in the paranoid score because local users with access to DRM render nodes may be able to exercise amdgpu command submission paths, but the checked address is kernel managed and not directly user supplied. The issue is not network reachable and there is no evidence of a UAF, OOB access, arbitrary write, or information leak. Impact should remain DoS only unless separate evidence shows that an attacker can control the fence address or turn the invariant violation into memory corruption.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)  SKIP CVE-2026-68251 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	WARNONLY SIMPLEFIX HARDWARE 	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=1
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate / Low-like**

## 2. Signal breakdown

Conservative signals:

* Reliable kernel crash / strong DoS: +1. `BUG_ON(addr & 0x3)` can crash the kernel if the SDMA fence address alignment invariant is violated.
* Requires admin/root/CAP or non-attacker-controlled internal state in typical deployments: -2. The checked `addr` appears kernel-managed by the amdgpu fence/ring path, not directly user supplied.
* Hard or unreliable trigger: -1. The patch does not show a normal user-controlled path to force misalignment.

Conservative total is treated as 0 after floor.

Paranoid signals:

* Local unprivileged trigger: +1. Local users with DRM render node access may be able to exercise amdgpu command submission paths.
* Reliable kernel crash / strong DoS: +1. If the invariant is reachable, `BUG_ON()` causes a host kernel crash.
* Hard or unreliable trigger: -1. No direct control over the fence address is demonstrated.

Paranoid total: 1.

No memory corruption signal is awarded. The patch shows assertion-to-warning hardening only. There is no UAF, OOB write, double free, type confusion, arbitrary write, page-cache corruption, or info leak.

## 3. Reachability analysis

The affected path is local to the AMDGPU SDMA ring fence emission code. It is not network reachable. A conservative interpretation requires privileged driver control, fault injection, or an internal driver/device error to violate the alignment invariant. A paranoid interpretation allows that an unprivileged local user with access to DRM render nodes may exercise related command submission paths, but the patched value is still kernel-managed and not shown to be attacker-controlled. Containers only matter if they expose the GPU render node into the container.

Call-site confidence: medium. The changed function is visible, but the full caller chain and attacker influence over `addr` are not provided.

## 4. Severity interpretation

This behaves like a Low-like or ordinary Moderate reliability issue, not an Important-class vulnerability. The realistic impact is local DoS through a kernel crash if an internal invariant is violated. The theoretical concern is limited to whether a local user can indirectly reach the bad alignment state, but the patch provides no evidence of memory corruption or privilege escalation.

## 5. One-sentence report phrase

An amdgpu SDMA fence alignment assertion used BUG_ON() and could crash the kernel if an internal fence address invariant was violated, but the value appears kernel-managed and the issue is not network reachable or supported by a memory corruption primitive.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This can be auto-closed for security triage unless separate evidence shows user control of the fence address or a downstream memory corruption primitive.

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

Patch: drm/amdgpu/sdma6.0: replace BUG_ON() with WARN_ON()
Commit: 2eb06c88426b6c8de602c608959f3a56ac51861e
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2eb06c88426b6c8de602c608959f3a56ac51861e

Commit description:

There's no need to crash the kernel for these cases.

Reviewed-by: Vitaly Prosyak <vitaly.prosyak@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit c17a508 )
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/amd/amdgpu/sdma_v6_0.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=2eb06c88426b6c8de602c608959f3a56ac51861e

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

The original Linux kernel CVE announcement for CVE-2026-68251 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68251

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:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: 0
  Paranoid ActionableScore: 1

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).