[CVE-2026-53190][LOW] drm/virtio: fix dma_fence refcount leak on error in virtio_gpu_dma_fence_wait()

[CVE-2026-53190][LOW] drm/virtio: fix dma_fence refcount leak on error in virtio_gpu_dma_fence_wait()

[AL-KERNEL]

CVE: CVE-2026-53190
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: drm/virtio: fix dma_fence refcount leak on error in virtio_gpu_dma_fence_wait()
Commit: 898bd0ccfed71651b881660c5d20ad73b5203174
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=898bd0ccfed71651b881660c5d20ad73b5203174
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53190
Analysis date: Mon, 29 Jun 2026 10:00:23 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A missing dma_fence_put() on an early error return in virtio_gpu_dma_fence_wait() can leak dma_fence chain references and allow a local DRM user to cause resource exhaustion DoS in affected virtio GPU guests.

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

The original Linux kernel CVE announcement for CVE-2026-53190 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53190

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-2026-53190	LOW	CHECK	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-772;*CWE-401;*CWE-664;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_fence reference leak can occur in the virtio GPU submit path because virtio_gpu_dma_fence_wait returns early from dma_fence_unwrap_for_each when virtio_gpu_do_fence_wait fails. The unwrap iterator takes an extra reference to itr.chain and the early return skipped the normal release path, so repeated failures can accumulate unreleased fence chain references. For the CVSS the PR:L is used because a local user or process with access to the virtio GPU DRM interface may be able to submit work and hit the error path, while no network reachability is involved. Impact is primarily denial of service through resource exhaustion. There is no concrete UAF, OOB access, arbitrary write, or information leak primitive indicated by this patch.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)  SKIP CVE-2026-53190  SKIP The Fixes patch not applied yet, so unlikely that actual: eba57fb5498f2858768321e64570caea188455b8 YES  NO NO unknown 	MAYBE	VIRT SIMPLEFIX LEAK HARDWARE LINUS MEMORY  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=2

## 1. ActionableScore

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

## 2. Signal breakdown

* Local unprivileged trigger: +1
  A local process with access to the virtio GPU DRM interface may be able to submit work and reach the error path.

* Availability impact realistic: +1
  Repeated failures can leak dma_fence chain references and may eventually cause resource exhaustion.

* No generic memory corruption: +0
  The patch fixes a missing dma_fence_put() on an error path. It does not show UAF, double-free, OOB write, arbitrary write, or object confusion.

* No privilege escalation plausible: +0
  The leaked reference keeps an object alive rather than freeing it too early, so there is no evident reclaim or stale pointer primitive.

* No remote reachability: +0
  This is a local DRM virtio GPU submit path, not a network-triggerable path.

## 3. Reachability analysis

The likely trigger is a local user or process that can access the virtio GPU DRM device and submit work involving dma_fence arrays. In many guest environments DRM render access can be available to non-root users, so PR:L is a reasonable CVSS interpretation. Namespaces or containers may matter only if the DRM device is passed through or exposed to the container. The bug requires virtio-gpu and an error from virtio_gpu_do_fence_wait(), so exploitation is not universal, but it is plausible in affected virtual GPU deployments.

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like resource leak rather than an Important kernel vulnerability. The theoretical worst case is denial of service through accumulated unreleased dma_fence references. There is no evidence of memory corruption, information disclosure, privilege escalation, or cross-boundary policy bypass.

## 5. One-sentence report phrase

A missing dma_fence_put() on an early error return in virtio_gpu_dma_fence_wait() can leak dma_fence chain references and allow a local DRM user to cause resource exhaustion DoS in affected virtio GPU guests.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This is a resource lifetime leak without evidence of UAF, stale pointer use, OOB access, arbitrary write, or privilege escalation.

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

Patch: drm/virtio: fix dma_fence refcount leak on error in virtio_gpu_dma_fence_wait()
Commit: 898bd0ccfed71651b881660c5d20ad73b5203174
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=898bd0ccfed71651b881660c5d20ad73b5203174

Commit description:

dma_fence_unwrap_for_each() internally calls dma_fence_unwrap_first()
which does cursor->chain = dma_fence_get(head), taking an extra
reference. On normal loop completion, dma_fence_unwrap_next()
releases this via dma_fence_chain_walk() -> dma_fence_put().

When virtio_gpu_do_fence_wait() fails and the function returns early
from inside the loop, the cursor->chain reference is never released.
This is the only caller in the entire kernel that does an early return
inside dma_fence_unwrap_for_each.

Add dma_fence_put(itr.chain) before the early return.

Cc: stable@vger.kernel.org
Fixes: eba57fb ("drm/virtio: Wait for each dma-fence of in-fence array individually")
Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>
Reviewed-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Link: https://patch.msgid.link/20260607090303.92423-1-vulab@iscas.ac.cn
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/virtio/virtgpu_submit.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=898bd0ccfed71651b881660c5d20ad73b5203174

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

The original Linux kernel CVE announcement for CVE-2026-53190 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53190

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).