[CVE-2026-80888][LOW] drm/vmwgfx: drop dma_buf reference on foreign-fd prime import

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

CVE: CVE-2026-80888
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: drm/vmwgfx: drop dma_buf reference on foreign-fd prime import
Commit: 619c3cfa88e09603a13d918f754808db2dda7057
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=619c3cfa88e09603a13d918f754808db2dda7057
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80888
Analysis date: Fri, 04 Sep 2026 15:08:42 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-80888 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80888

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: YES

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

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

CVE-2026-80888	LOW	https://www.kernelcve.org/list/?q=CVE-2026-80888 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-401;*CWE-772;**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 'A dma_buf reference leak in the vmwgfx PRIME import path occurs because ttm_prime_fd_to_handle returns ENOSYS for a foreign prime fd without dropping the reference acquired by dma_buf_get. A local client can repeat the DRM_VMW_GB_SURFACE_REF or DRM_VMW_GB_SURFACE_REF_EXT path with non vmwgfx dma_buf fds and indefinitely pin foreign exporter GEM resources. For the CVSS the PR:L is used because an unprivileged local renderD client can reach the affected DRM ioctl path in typical deployments. The issue is not network reachable and requires local access to the DRM render device. Impact is denial of service through resource exhaustion. There is no evidence of UAF, OOB access, arbitrary write, information disclosure, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)	YES	SIMPLEFIX LEAK ERRORPATH HARDWARE LINUS MEMORY  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	NO	NO	checked

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

ActionableScore=2

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

2. Signal breakdown
* Local unprivileged trigger: +1. The commit explicitly says any unprivileged renderD client can pass a non-vmwgfx PRIME fd through DRM_VMW_GB_SURFACE_REF or DRM_VMW_GB_SURFACE_REF_EXT.
* Availability impact realistic: +1. Repeated calls leak dma_buf references and can indefinitely pin foreign GEM resources, causing resource exhaustion or GPU resource pressure.
* No generic memory corruption: +0. The patch fixes a missing dma_buf_put on an error path, not UAF, double free, OOB write, type confusion, or arbitrary write.
* No privilege escalation plausible: +0. There is no supported path to code execution, credential modification, object replacement, or security-boundary bypass.
* No remote reachability: +0. The affected path is a local DRM render node ioctl path.

3. Reachability analysis
The bug is reachable by a local unprivileged user if the vmwgfx DRM render device is exposed and the user can obtain or pass a foreign dma_buf fd. Containers may matter if DRM render nodes are delegated into the container, but this still remains a local device access issue rather than a network issue. The affected path is not universally enabled on all Linux systems, but it is a normal interface on VMware graphics deployments using vmwgfx.

4. Severity interpretation
This behaves like an ordinary Moderate or Low-like local resource exhaustion issue. The realistic impact is repeated reference leakage and indefinite pinning of GEM resources, not kernel memory corruption or LPE. The paranoid interpretation can raise CVSS availability to A:H for sustained abuse, but the ActionableScore should remain low because the primitive is only a reference leak and does not cross into UAF, overwrite, info leak, or privilege escalation.

5. One-sentence report phrase
A local unprivileged renderD client can repeatedly trigger a missing dma_buf_put error path in vmwgfx PRIME import, leaking dma_buf references and pinning foreign GEM resources until resource exhaustion occurs.

6. Manual review recommendation
NO MANUAL CHECK REQUIRED COULD BE AUTOCLOSED. This is a resource leak without evidence of memory corruption, information disclosure, privilege escalation, or network reachability.

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

Patch: drm/vmwgfx: drop dma_buf reference on foreign-fd prime import
Commit: 619c3cfa88e09603a13d918f754808db2dda7057
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=619c3cfa88e09603a13d918f754808db2dda7057

Commit description:

ttm_prime_fd_to_handle() returns -ENOSYS when the imported fd's
dma_buf->ops do not match the ttm_object_device's ops, but does so
without releasing the reference acquired by dma_buf_get().  Any
unprivileged renderD client passing a non-vmwgfx prime fd through the
DRM_VMW_GB_SURFACE_REF{,_EXT} path leaks one dma_buf reference per
call and indefinitely pins the foreign exporter's GEM resources.

Funnel the error path through the existing dma_buf_put() so the
reference is always dropped.

Fixes: 65981f7 ("drm/ttm: Add a minimal prime implementation for ttm base objects")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4.7
Signed-off-by: Zack Rusin <zack.rusin@broadcom.com>
Reviewed-by: Ian Forbes <ian.forbes@broadcom.com>
Link: https://patch.msgid.link/20260505222728.519626-6-zack.rusin@broadcom.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/vmwgfx/ttm_object.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=619c3cfa88e09603a13d918f754808db2dda7057

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

The original Linux kernel CVE announcement for CVE-2026-80888 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80888

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: 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).