[CVE-2026-63847][MODERATE REGULAR] drm/amdgpu/jpeg: set no_user_fence for JPEG v2.5 ring [ Upstream

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

CVE: CVE-2026-63847
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: drm/amdgpu/jpeg: set no_user_fence for JPEG v2.5 ring [ Upstream
Commit: 63691e396105611173072ad548fc2b68831ecf23
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=63691e396105611173072ad548fc2b68831ecf23
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63847
Analysis date: Sun, 19 Jul 2026 11:20:51 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Ordinary Moderate / Low-like. Not an Actionable Moderate candidate
Manual review required: NO

Summary:
AMDGPU JPEG v2.5 and v2.6 rings accepted unsupported 64 bit user fence command submissions, allowing a local DRM render node user to potentially trigger JPEG ring failure, GPU reset, or degraded GPU availability.

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

The original Linux kernel CVE announcement for CVE-2026-63847 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63847

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: 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-2026-63847	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-754;**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 'AMDGPU JPEG v2.5 and v2.6 rings could accept command submissions with user fences even though these JPEG rings do not support 64 bit user fence writes. A local process with access to the DRM render node could submit such a command stream and trigger incorrect fence handling on the JPEG ring. The likely impact is denial of service through a failed job, ring hang, GPU reset, or degraded GPU availability. For the CVSS the PR:L is used because a local user or process with DRM render node access can submit command streams, while full administrator privileges are not normally required. The issue is not network reachable and there is no clear evidence of kernel memory corruption, information disclosure, or privilege escalation from this patch context.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like. Not an Actionable Moderate candidate (with actual score 3)  SKIP CVE-2026-63847 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	SIMPLEFIX HARDWARE  INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=3
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 3
* Final recommended bucket: **Ordinary Moderate / Low-like. Not an Actionable Moderate candidate**::

## 2. Signal breakdown

* Local unprivileged trigger: +1
  A local process with access to the AMDGPU DRM render node can submit command streams. This typically does not require full root privileges on desktop or GPU-enabled systems.

* Availability impact realistic: +1
  Unsupported user fence submissions on JPEG rings may cause failed jobs, ring hangs, GPU reset, or degraded GPU availability.

* Paranoid reliable device DoS concern: +1
  In the higher interpretation, repeated submissions could make GPU availability loss more reliable or persistent for affected hardware.

* No memory corruption signal: +0
  The patch only sets `.no_user_fence = true` to reject unsupported CS submissions. It does not show UAF, OOB write, arbitrary write, refcount misuse, type confusion, or page ownership corruption.

* No LPE signal: +0
  There is no concrete primitive suggesting privilege escalation.

* No confidentiality or integrity signal: +0
  The issue affects unsupported fence handling and likely availability only.

* No high-control device API bonus: +0
  DRM command submission is a rich device API, but this patch does not show attacker control over kernel object lifetime, reclaim, callback targets, refcounts, DMA mappings, or page ownership.

## 3. Reachability analysis

The bug is locally reachable by users or processes that can access the AMDGPU render node and submit JPEG ring command streams. It is not network reachable. Namespaces or containers matter only if GPU render node access is delegated into the container. The path is hardware-dependent and applies to affected AMDGPU JPEG v2.5 and v2.6 rings, but when such hardware and render-node access exist, triggering does not appear to require administrator privileges.

Call-site confidence: medium. The patch does not include the CS rejection path, but the ring flag name and AMDGPU convention strongly indicate that `.no_user_fence` blocks user-fence submissions for unsupported rings.

## 4. Severity interpretation

This behaves like a local GPU availability issue, not an Important-class kernel vulnerability. The realistic impact is DoS against the GPU ring or driver recovery path. Theoretical escalation is not supported by the patch context because there is no demonstrated memory corruption, attacker-controlled overwrite, stale pointer, or shared-page corruption primitive.

## 5. One-sentence report phrase

AMDGPU JPEG v2.5 and v2.6 rings accepted unsupported 64 bit user fence command submissions, allowing a local DRM render node user to potentially trigger JPEG ring failure, GPU reset, or degraded GPU availability.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This can be handled as a low-priority local GPU DoS unless the affected product treats local GPU availability loss as security-critical or exposes AMDGPU render nodes to untrusted tenants.

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

Patch: drm/amdgpu/jpeg: set no_user_fence for JPEG v2.5 ring [ Upstream
Commit: 63691e396105611173072ad548fc2b68831ecf23
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=63691e396105611173072ad548fc2b68831ecf23

Changed files:
  drivers/gpu/drm/amd/amdgpu/jpeg_v2_5.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=63691e396105611173072ad548fc2b68831ecf23

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

The original Linux kernel CVE announcement for CVE-2026-63847 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63847

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: 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).