[CVE-2026-68102][LOW] drm/amdgpu: fix aperture mapping leak

[CVE-2026-68102][LOW] drm/amdgpu: fix aperture mapping leak

[AL-KERNEL]

CVE: CVE-2026-68102
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: drm/amdgpu: fix aperture mapping leak
Commit: 67bc3647e418e23dc0d17604bdba634a73de809f
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=67bc3647e418e23dc0d17604bdba634a73de809f
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68102
Analysis date: Mon, 10 Aug 2026 10:59:05 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-68102 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68102

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.

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

CVE-2026-68102	LOW	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:H/UI:N/S:U/C:N/I:N/A:H';*CWE-772;*CWE-401;CWE-404;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.4';DESCR 'amdgpu can leave an aperture mapping behind during normal driver unload because drm_dev_unplug makes drm_dev_enter fail in amdgpu_ttm_fini before iounmap of aper_base_kaddr is reached. On connected_to_cpu hardware this can orphan a WB PAT interval entry and a later reload can try to remap the same aperture as WC during IP discovery, causing a cache attribute conflict and driver discovery failure. For the CVSS the PR:H is used because reliable triggering normally requires administrative control over driver unload reload or device removal. The issue is local only and not network reachable. Impact is denial of service for the GPU device or driver reload path, with no evidence of memory corruption, information disclosure, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 0)  SKIP CVE-2026-68102 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	INIT NOMEMCHK LEAK HARDWARE 	-	-	checked

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

ActionableScore=0

1. **ActionableScore**
* Conservative score: 0
* Paranoid score: 0
* Final recommended bucket: **Ordinary Moderate / Low-like**

2. **Signal breakdown**
* Availability impact realistic: +1. The stale PAT mapping can prevent later amdgpu reload or IP discovery, causing GPU driver availability loss.
* Requires admin/root/CAP_* in typical deployments: -2. Reliable triggering normally requires driver unload/reload, PCI device removal, or equivalent host administrative control.
* Rare or configuration-dependent path: -1. The described failure depends on normal driver unload followed by reload and especially the connected_to_cpu aperture mapping / PAT conflict scenario.
* No memory corruption signal: +0. The patch fixes resource ownership and cleanup of mappings, not UAF, OOB write, double free, type confusion, arbitrary write, or page-cache corruption.
* No LPE signal: +0. There is no supported privilege escalation primitive.
* No remote or firmware-mediated trigger: +0. The path is local device management, not network reachable.
* Call-site confidence: high. The relevant cleanup and init paths are visible in the supplied diff.

3. **Reachability analysis**
The bug is reachable through amdgpu driver teardown and reload paths. In typical deployments, this requires host-root or equivalent administrative control over module unload, PCI device removal, GPU reset workflows, or driver lifecycle management. Containers and namespaces usually do not lower the privilege requirement because direct GPU driver unload/reload is not delegated to ordinary container users. The affected driver is broadly deployed, but the vulnerable condition is not a normal unprivileged runtime path and depends on specific hardware and reload behavior.

4. **Severity interpretation**
This behaves like a low-end Moderate or Low-like operational availability bug. The realistic impact is GPU driver reload failure or device unavailability due to an orphaned mapping / PAT cache attribute conflict. The patch does not support memory corruption, confidentiality impact, integrity impact, privilege escalation, or cross-boundary access. Theoretical severity should not be raised beyond DoS because the resource leak is a mapping cleanup problem, not a corruptible attacker-controlled kernel object lifetime primitive.

5. **One-sentence report phrase**
amdgpu may leave an aperture mapping and stale PAT interval behind during privileged driver unload, causing later reload or IP discovery failure and resulting in local administrative denial of service for the GPU device.

6. **Manual review recommendation**
NO MANUAL CHECK NEEDED

Reason: this is a local privileged resource cleanup issue with low practical exposure, no memory corruption primitive, no unprivileged trigger, no network reachability, and no plausible LPE path.

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

Patch: drm/amdgpu: fix aperture mapping leak
Commit: 67bc3647e418e23dc0d17604bdba634a73de809f
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=67bc3647e418e23dc0d17604bdba634a73de809f

Commit description:

amdgpu_pci_remove() calls drm_dev_unplug() before invoking the driver
fini routines. This causes drm_dev_enter() in amdgpu_ttm_fini() to
always return false, so iounmap(aper_base_kaddr) never runs on normal
driver unload, leaving an orphaned entry in the x86 PAT interval tree.

On connected_to_cpu hardware, the aperture is mapped write-back (WB) via
ioremap_cache(). On reload, IP discovery calls memremap(..., MEMREMAP_WC)
over the same range. The WC vs WB conflict causes:

  ioremap error for 0x..., requested 0x1, got 0x0
  amdgpu: discovery failed: -2

Fix by switching to devres-managed mappings so cleanup is guaranteed
regardless of drm_dev_enter() state:

- connected_to_cpu path: devm_memremap(MEMREMAP_WB). For
  IORESOURCE_SYSTEM_RAM ranges this takes the try_ram_remap() shortcut,
  returning __va(offset) from the existing kernel direct map. No new
  ioremap VA or PAT entry is created, so there is nothing to orphan.

- dGPU path: devm_ioremap_wc() registers iounmap() as a devres action,
  guaranteeing cleanup at device_del() time.

Also remove iounmap(aper_base_kaddr) from amdgpu_device_unmap_mmio()
since the mapping is now devres-owned.

v2: Remove redundant x86_64 guard (Lijo)

Fixes: 9d0af8b ("drm/amdgpu: pre-map device buffer as cached for A+A config")
Signed-off-by: Asad Kamal <asad.kamal@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit d871e99 )
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=67bc3647e418e23dc0d17604bdba634a73de809f

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

The original Linux kernel CVE announcement for CVE-2026-68102 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68102

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:H/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.4

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: 0

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).