[CVE-2026-68240][LOW] drm/gpusvm: publish dpagemap early to avoid device mapping leak on error

[CVE-2026-68240][LOW] drm/gpusvm: publish dpagemap early to avoid device mapping leak on error

[AL-KERNEL]

CVE: CVE-2026-68240
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: drm/gpusvm: publish dpagemap early to avoid device mapping leak on error
Commit: e8362523fd1b61712f7d996802f9b5dee545c7e6
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e8362523fd1b61712f7d996802f9b5dee545c7e6
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68240
Analysis date: Mon, 10 Aug 2026 16:38:08 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A local DRM/GPU SVM error path can leak device mappings when drm_gpusvm_get_pages() fails after partial mapping, potentially allowing resource exhaustion but not showing a concrete confidentiality, integrity, or privilege escalation primitive.

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

The original Linux kernel CVE announcement for CVE-2026-68240 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68240

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-2026-68240	LOW	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:N/I:N/A:H';*CWE-772;*CWE-401;**CWE-400;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'A device mapping leak in DRM/GPU SVM can occur when drm_gpusvm_get_pages maps one or more device pages and then fails on a later page before svm_pages dpagemap is published. This makes the error cleanup path skip device_unmap for mappings already created, so repeated failures may accumulate leaked GPU or IOMMU device mappings and cause resource exhaustion. For the CVSS the PR:L is used because a local process with access to the DRM/GPU SVM interface can plausibly trigger the error path, while no network or unauthenticated remote path is indicated. The issue is not directly network reachable and requires local interaction with the GPU memory management interface. Impact is denial of service through resource exhaustion. No direct confidentiality or integrity primitive is visible from the code change context because the bug is a cleanup resource leak rather than a proven stale mapping use primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)  SKIP CVE-2026-68240 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: f70da6f99d4f40c5f481c92e3b65d5e36eaa6dc9 YES  NO NO unknown 	MAYBE	SIMPLEFIX LEAK HARDWARE 	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=2
ActionableScoreLower=1

## 1. ActionableScore

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

## 2. Signal breakdown

Triggered signals:

* Local unprivileged trigger: +1
  A local process with access to the DRM/GPU SVM interface may be able to trigger the error path. This is plausible through normal GPU device access rather than requiring full host root.

* Availability impact realistic: +1 in paranoid scoring only
  Repeated failures may accumulate leaked device mappings and potentially exhaust GPU/IOMMU or related mapping resources. This is resource exhaustion, not memory corruption.

Subtracting signals:

* Hard or special triggering conditions: -1 in conservative scoring
  The bug requires partial success followed by a later failure in drm_gpusvm_get_pages(), for example mixed page handling with ctx->allow_mixed false. A single ordinary call is not clearly enough to cause system-wide failure.

Not awarded:

* No remote/network reachability.
* No strong memory corruption primitive.
* No UAF, double free, OOB write, arbitrary write, callback corruption, or type confusion shown.
* No privilege escalation plausibility beyond generic resource exhaustion.
* No confidentiality or integrity impact supported by the patch.

## 3. Reachability analysis

The likely trigger is a local process interacting with DRM/GPU SVM memory management. On systems where GPU render nodes or relevant DRM interfaces are available to unprivileged users, PR is effectively local low privilege. Namespaces do not obviously create a separate remote or container escape path, but containerized workloads with GPU device access could potentially trigger the same local device path.

The issue is not default reachable over the network. It also depends on a GPU/SVM configuration and on reaching an error path after at least one device page has already been mapped. This makes practical exploitation more like repeated local resource leakage than an immediate crash or corruption primitive.

Call-site confidence: medium. The provided diff shows the mapping and cleanup relation directly, but not all callers or deployment-specific GPU access controls.

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like resource leak. The patch fixes an error-path cleanup problem where device mappings created by device_map() were not later released by device_unmap() because svm_pages->dpagemap was still NULL.

The theoretical worst case is sustained local resource exhaustion if the failing path can be repeated. The realistic evidence does not show memory corruption, stale mapping use as an access primitive, unauthorized memory access, privilege escalation, or cross-security-boundary data modification. Therefore it should not be treated as an Important-class candidate based on the supplied patch.

## 5. One-sentence report phrase

A local DRM/GPU SVM error path can leak device mappings when drm_gpusvm_get_pages() fails after partial mapping, potentially allowing resource exhaustion but not showing a concrete confidentiality, integrity, or privilege escalation primitive.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This can likely be auto-closed or handled as low-priority Moderate unless product-specific evidence shows unprivileged users can reliably exhaust GPU/IOMMU mappings quickly or that leaked mappings remain usable as a stale access primitive.

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

Patch: drm/gpusvm: publish dpagemap early to avoid device mapping leak on error
Commit: e8362523fd1b61712f7d996802f9b5dee545c7e6
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e8362523fd1b61712f7d996802f9b5dee545c7e6

Commit description:

drm_gpusvm_get_pages() only stored the local dpagemap into
svm_pages->dpagemap on the success path. If a later page failed (e.g.
-EOPNOTSUPP when ctx->allow_mixed is false) and jumped to err_unmap,
svm_pages->dpagemap was still NULL, so __drm_gpusvm_unmap_pages() skipped
device_unmap() and leaked the device mappings already created.

Assign svm_pages->dpagemap when the first device page is mapped so the
err_unmap path can device_unmap() those mappings.

This issue was found by Sashiko AI review.

Fixes: f70da6f ("drm/gpusvm: pull out drm_gpusvm_pages substructure")
Cc: stable@vger.kernel.org
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Honglei Huang <honghuan@amd.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patch.msgid.link/20260701062800.409248-4-honghuan@amd.com
[ Adjusted for 6.18.y: drop drm_pagemap_get()/drm_pagemap_put() around the
  svm_pages->dpagemap assignment; that reference counting is not present in
  6.18 where the field is not refcounted (unmap path only clears it). ]
Signed-off-by: Honglei Huang <honghuan@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Changed files:
  drivers/gpu/drm/drm_gpusvm.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=e8362523fd1b61712f7d996802f9b5dee545c7e6

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

The original Linux kernel CVE announcement for CVE-2026-68240 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68240

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:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: 1
  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).