[CVE-2026-68236][IMPORTANT] drm/amd/display: set new_stream to NULL after release

[CVE-2026-68236][IMPORTANT] drm/amd/display: set new_stream to NULL after release

[AL-KERNEL]

CVE: CVE-2026-68236
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: drm/amd/display: set new_stream to NULL after release
Commit: ba8bf1dcbb44773e7a0fd13b42925c644e0d5e76
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ba8bf1dcbb44773e7a0fd13b42925c644e0d5e76
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68236
Analysis date: Mon, 10 Aug 2026 10:54:58 -0400
ActionableScore: 7
ActionableScore lower bound: 5
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-68236 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68236

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: IMPORTANT
Manual review required: YES

A detailed explanation of the methodology and priority rules is included
at the end of this message.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-68236	IMPORTANT	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';CWE-415;*CWE-416;*CWE-672;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A double release in the AMD display CRTC update path can occur because new_stream is released in the skip_modeset path but the dangling pointer is left non NULL. If a later failure path is reached, for example during color management handling, the fail cleanup can call dc_stream_release on the same object again and create a use after free condition. For the CVSS the PR:L is selected because triggering requires local access to the DRM or KMS control path rather than remote packet delivery. The issue is not network reachable and normally requires a local graphical session, DRM master style access, or a process with delegated display control. Impact is at least local denial of service via kernel crash and in the worst case may allow confidentiality or integrity impact due to kernel memory corruption. For the paranoid score, the highest still defensible interpretation is local memory corruption with CIA:HHH because the bug class is double release and potential UAF.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7)	MAYBE	DANGER ERRORPATH UAF HARDWARE KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7	-	-	guess

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

ActionableScore=7
ActionableScoreLower=5

1. ActionableScore
* Conservative score: 5
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

2. Signal breakdown
* Local unprivileged trigger: +1. Triggering is local through DRM/KMS display control paths, not network traffic.
* Memory corruption, strong corruption primitive: +2. The patch explicitly fixes a double release and potential use after free.
* Real lifetime corruption: +1. The bug is a stale pointer after dc_stream_release() followed by possible second release on the fail path.
* Reliable kernel crash / strong DoS: +1. A double release in kernel display code can plausibly crash the kernel.
* Broad/default/common subsystem: +1. AMDGPU display is common on affected desktop and workstation systems, although hardware dependent.
* Hard or unreliable race / special conditions: -1. Triggering requires the skip_modeset path plus a later error path such as color management failure.
* Paranoid C/I impact: +2. For the paranoid score, confidentiality and integrity impact are treated as plausible because this is a kernel UAF/double release class bug, but no controlled reclaim or overwrite primitive is demonstrated.

3. Reachability analysis
A local user or local process with access to DRM/KMS display control can potentially trigger the affected path. This usually means an active graphical session, DRM master style access, compositor involvement, or delegated display control. It is not remotely reachable over the network. Containers and namespaces generally do not expose this path unless DRM devices are passed through or delegated. The path is hardware and configuration dependent because it requires AMD display code and a specific CRTC update/error sequence.

Call-site confidence: medium. The commit message clearly describes the second release on the fail path, but the full fail label and all call sites are not included in the provided patch excerpt.

4. Severity interpretation
This is more than an ordinary Moderate cleanup because it is an explicit kernel double release / potential UAF in a local device control path. Realistic exploitation evidence is limited, because the patch does not show attacker-controlled reclaim, type confusion, callback control, or arbitrary write. Conservatively it is an Actionable Moderate. Paranoid handling as a Strong Important candidate is defensible for manual review because kernel lifetime corruption in DRM/KMS paths has possible LPE relevance even when the immediate demonstrated impact is DoS.

5. One-sentence report phrase
A double release in the AMD display CRTC update path can leave new_stream dangling after dc_stream_release(), allowing a later error cleanup path to release the same object again and potentially cause kernel UAF or crash.

6. Manual review recommendation
MANUAL CHECK REQUIRED. YES REQUIRES MANUAL CHECK.
Reason: explicit double release and potential UAF in kernel code, local PR:L reachability, and plausible but unproven privilege escalation impact.

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

Patch: drm/amd/display: set new_stream to NULL after release
Commit: ba8bf1dcbb44773e7a0fd13b42925c644e0d5e76
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ba8bf1dcbb44773e7a0fd13b42925c644e0d5e76

Commit description:

In dm_update_crtc_state(), the skip_modeset path releases new_stream
via dc_stream_release() but does not set the pointer to NULL.

If a later error (e.g., color management failure) triggers the fail
label, the error path calls dc_stream_release() again on the same
dangling pointer, causing a double release and potential use-after-free.

Fix this by setting new_stream to NULL after the initial release.

Fixes: 9b690ef ("drm/amd/display: Avoid full modeset when not required")
Signed-off-by: WenTao Liang <vulab@iscas.ac.cn>
Reviewed-by: George Zhang <george.zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 99f3af1 )
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.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=ba8bf1dcbb44773e7a0fd13b42925c644e0d5e76

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

The original Linux kernel CVE announcement for CVE-2026-68236 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68236

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:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 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: 5
  Paranoid ActionableScore: 7

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: IMPORTANT
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): IMPORTANT

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).