[CVE-2026-52987][IMPORTANT] drm/amdgpu: avoid double drm_exec_fini() in userq validate [ Upstream

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

CVE: CVE-2026-52987
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: drm/amdgpu: avoid double drm_exec_fini() in userq validate [ Upstream
Commit: c7c3ae7c01e5a0742b93cb9b40800bdd7f811e38
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c7c3ae7c01e5a0742b93cb9b40800bdd7f811e38
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52987
Analysis date: Fri, 26 Jun 2026 16:08:47 -0400
ActionableScore: 8
ActionableScore lower bound: 6
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A local AMDGPU userqueue validation error path can call `drm_exec_fini()` twice on the same exec object after a `get_user_pages` failure, creating a double-free / UAF candidate with at least kernel crash impact and possible privilege-escalation concern.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-52987 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52987

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-52987	IMPORTANT	CHECK	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 finalization bug in the AMDGPU userqueue validation path can occur when drm_exec_fini() is called before HMM range processing and amdgpu_ttm_tt_get_user_pages() later fails. The error path can then call drm_exec_fini() again on the same exec object, while drm_exec_fini() may free exec objects and finalize lock state. This is a local kernel memory corruption candidate rather than a simple warning or NULL dereference. For the CVSS the PR:L is used because a local process with access to the AMDGPU DRM render interface may be able to exercise userqueue validation without full administrative privileges. The issue is not network reachable. Impact is at least a local denial of service via kernel crash and in worst case may allow confidentiality or integrity impact due to double free or use after free behavior, so it should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 8)  SKIP CVE-2026-52987  SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	SIMPLEFIX ERRORPATH HARDWARE  KPANIC INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=8
ActionableScoreLower=6

## 1. ActionableScore

* Conservative score: 6
* Paranoid score: 8
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. A local process with access to the AMDGPU DRM render interface may reach userqueue validation without full root privileges.
* Memory corruption, strong corruption primitive: +2. The patch prevents a second call to `drm_exec_fini()` on the same object, and the commit states that this function frees `exec->objects` and finalizes related state.
* Real lifetime corruption: +1. This is a double finalization / double free lifetime bug.
* Reliable kernel crash / strong DoS: +1. A double free or finalized lock state reuse can plausibly crash the kernel.
* Weak LPE concern: +1. Double free / UAF candidates in kernel heap state can sometimes become privilege escalation, but no concrete reclaim or overwrite primitive is shown.
* Hard or unreliable trigger condition: -1. The path requires `new_addition == true` and a later `amdgpu_ttm_tt_get_user_pages()` failure after `drm_exec_fini()` has already run.
* Privileged kernel/device-management memory corruption path: +1. The corruption occurs inside a trusted GPU memory-management / DRM execution context.

Paranoid additions:

* Confidentiality impact plausible: +1. If the double free becomes exploitable as UAF or object confusion, kernel data exposure is possible.
* Integrity impact plausible: +1. If heap state is controllable enough, corruption could affect kernel objects or privilege state.

## 3. Reachability analysis

The bug is local, not network reachable. The likely attacker is a local user or process that can access AMDGPU DRM userqueue functionality, typically through a render node or GPU device file depending on system policy.

This should not be scored as PR:H by default, because DRM render nodes are commonly exposed to non-root desktop, compute, container, or service workloads. Namespaces or containers can reduce the effective privilege requirement if GPU device access is delegated into the container.

The trigger is not completely trivial. It needs the `new_addition` validation path and an error from `amdgpu_ttm_tt_get_user_pages()` after `drm_exec_fini()` already ran. That makes exploitation more complex than a simple ioctl crash, but the underlying primitive is still a real double finalization of kernel-managed state.

## 4. Severity interpretation

This behaves stronger than an ordinary Moderate because the patch fixes a real double-finalization path where a non-idempotent cleanup function can free internal objects twice. Realistically, the most likely immediate impact is local kernel crash or GPU-driver-triggered DoS.

Theoretical exploitation could extend beyond DoS because double free and UAF-style bugs are memory lifetime corruption primitives. However, the patch does not demonstrate controlled reclaim, arbitrary write, or a reliable LPE chain. Therefore the conservative score is Actionable Moderate, while the paranoid score is a Strong Important candidate that should not be auto-closed.

## 5. One-sentence report phrase

A local AMDGPU userqueue validation error path can call `drm_exec_fini()` twice on the same exec object after a `get_user_pages` failure, creating a double-free / UAF candidate with at least kernel crash impact and possible privilege-escalation concern.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

This is a kernel double-free / lifetime-corruption candidate in a local DRM GPU interface that may be reachable without full administrative privileges. The practical LPE primitive is not proven, but the bug class and subsystem exposure justify manual review.

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

Patch: drm/amdgpu: avoid double drm_exec_fini() in userq validate [ Upstream
Commit: c7c3ae7c01e5a0742b93cb9b40800bdd7f811e38
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c7c3ae7c01e5a0742b93cb9b40800bdd7f811e38

Changed files:
  drivers/gpu/drm/amd/amdgpu/amdgpu_userq.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=c7c3ae7c01e5a0742b93cb9b40800bdd7f811e38

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

The original Linux kernel CVE announcement for CVE-2026-52987 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52987

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: 6
  Paranoid ActionableScore: 8

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).