[CVE-2026-80728][MODERATE 7.0] Revert "drm/amdgpu: fix aperture mapping leak"

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

CVE: CVE-2026-80728
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: Revert "drm/amdgpu: fix aperture mapping leak"
Commit: 7380f1bfe9d7ed3a4ca9d99a5c4df840fff9af2a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7380f1bfe9d7ed3a4ca9d99a5c4df840fff9af2a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80728
Analysis date: Thu, 03 Sep 2026 04:43:53 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
AMDGPU probe failure or rollback can leave teardown code writing through a stale aperture mapping pointer after devres unmapped it, causing a kernel page fault and local DoS in a privileged or delegated GPU device-management scenario.

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

The original Linux kernel CVE announcement for CVE-2026-80728 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80728

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 7.0
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-2026-80728	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-80728 CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';*CWE-672;CWE-825;*CWE-664;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'An AMDGPU probe failure or rollback can hit a kernel page fault because the aperture mapping may be released before the DRM device release path finishes. IP software finalization callbacks such as vcn_v4_0_sw_fini can then access fw_shared through a stale pointer derived from aper_base_kaddr after the mapping was already unmapped. For the CVSS the PR:L is used in the paranoid score because some deployments may delegate GPU reset, device binding, or driver control to a service account, container root, or reduced capability administrator rather than full host root. The issue is not network reachable and requires local control over the affected device or driver lifecycle. Impact is at least denial of service via kernel crash. In the worst still defensible case it may have limited confidentiality or integrity impact because the bug involves a stale kernel mapping pointer and a write in teardown context, so it should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)  SKIP CVE-2026-80728 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	INIT NOMEMCHK LEAK HARDWARE  INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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

ActionableScore=5
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Weak/indirect corruption candidate: +1. The bug is a stale `aper_base_kaddr` mapping pointer used after the aperture was already unmapped.
* Real lifetime corruption: +1. The core issue is incorrect lifetime ordering between devres teardown and DRM device release.
* Reliable kernel crash / strong DoS: +1. The commit shows a concrete kernel page fault in `vcn_v4_0_sw_fini`.
* Privileged kernel/device-management memory corruption path: +1. The stale access occurs in AMDGPU teardown / probe rollback, a trusted device-management path.
* Availability impact realistic: +1. The demonstrated failure is a kernel page fault during driver cleanup.
* Requires admin/root/device-management privileges in typical deployments: -2. Reliable triggering usually requires driver probe failure, bind/unbind, reset, rollback, or comparable control over the GPU driver lifecycle.

Paranoid additions / adjustments:

* Firmware-mediated external influence: +1. The trigger depends on probe failure / rollback and may be influenced by device or firmware behavior, although this is not remote network reachability.
* Reduced-capability admin interpretation reduces the privilege penalty. GPU reset, device binding, passthrough, or recovery control may be delegated to a service account, container root, or limited operator in some deployments.

## 3. Reachability analysis

The issue is local and device-lifecycle dependent. A typical attacker would need administrative or delegated control over AMDGPU probe, rollback, reset, or driver binding behavior. It is not network reachable. Namespaces or containers matter only if GPU device control, PCI binding, DRM device management, or reset operations are delegated into that environment. The affected path is not a common unprivileged syscall path. Triggering requires AMDGPU hardware and a probe failure or rollback condition, but once that state is reached the crash path described by the commit appears concrete.

## 4. Severity interpretation

This behaves more like Actionable Moderate than ordinary Low because the patch fixes a real stale mapping lifetime bug in a kernel driver teardown path with a demonstrated kernel page fault. It is not a Strong Important candidate by default because there is no shown attacker-controlled reclaim, arbitrary write, type confusion, controlled target selection, or practical privilege escalation chain. The theoretical concern is that a stale kernel mapping pointer is used for a write in teardown context, but the realistic evidence supports kernel crash / DoS more strongly than LPE.

## 5. One-sentence report phrase

AMDGPU probe failure or rollback can leave teardown code writing through a stale aperture mapping pointer after devres unmapped it, causing a kernel page fault and local DoS in a privileged or delegated GPU device-management scenario.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is not merely a warning or resource leak. It is a stale mapping lifetime bug with a write through a pointer derived from an unmapped aperture in a privileged kernel driver path, so manual review is justified even though the demonstrated impact is mainly DoS.

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

Patch: Revert "drm/amdgpu: fix aperture mapping leak"
Commit: 7380f1bfe9d7ed3a4ca9d99a5c4df840fff9af2a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7380f1bfe9d7ed3a4ca9d99a5c4df840fff9af2a

Commit description:

devres teardown is LIFO. The aperture devres node was registered after
the DRM device node, so devres_release_all() unmaps the aperture before
the DRM device release callback fires amdgpu_device_fini_sw(). IP
sw_fini callbacks (e.g. vcn_v4_0_sw_fini) write to fw_shared through a
pointer derived from aper_base_kaddr, causing a kernel page fault on
probe failure / rollback:

  BUG: unable to handle page fault ... PMD 0
  RIP: vcn_v4_0_sw_fini+0x7b/0x170 [amdgpu]
  Call Trace:
    amdgpu_device_fini_sw
    amdgpu_driver_release_kms
    devm_drm_dev_init_release
    devres_release_all

This reverts commit d871e99 .

Fixes: d871e99 ("drm/amdgpu: fix aperture mapping leak")
Reported-by: Yuansheng Mao <yuansheng.mao@amd.com>
Signed-off-by: Asad Kamal <asad.kamal@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 336e0cd )
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
  drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.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=7380f1bfe9d7ed3a4ca9d99a5c4df840fff9af2a

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

The original Linux kernel CVE announcement for CVE-2026-80728 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80728

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:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 5.8

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: 3
  Paranoid ActionableScore: 5

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 7.0

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).