[CVE-2026-80700][MODERATE 7.0] drm/vmwgfx: validate external BO copy bounds for both stride paths

[CVE-2026-80700][MODERATE 7.0] drm/vmwgfx: validate external BO copy bounds for both stride paths

[AL-KERNEL]

CVE: CVE-2026-80700
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: drm/vmwgfx: validate external BO copy bounds for both stride paths
Commit: 4e0f669e2951b742239c6fe847fcc406fe78748d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4e0f669e2951b742239c6fe847fcc406fe78748d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80700
Analysis date: Fri, 28 Aug 2026 04:07:25 -0400
ActionableScore: 8
ActionableScore lower bound: 7
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A bounds validation flaw in vmwgfx external BO copy allows a local DRM user to craft imported framebuffer state that can make memcpy read or write past the end of mapped buffer objects, causing kernel memory corruption and likely DoS with possible privilege escalation requiring manual review.

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

The original Linux kernel CVE announcement for CVE-2026-80700 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80700

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-80700	MODERATE	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-787;CWE-125;CWE-190;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.8';DESCR 'A bounds validation flaw in vmwgfx external BO copy can allow an out-of-bounds read or write when copying imported dma-buf backed framebuffers. The vulnerable path trusts caller controlled offsets, strides, and height from plane state, and a crafted atomic commit on a configured CRTC can make memcpy operate past the end of the source or destination vmap. For the CVSS the PR:L is used because reliable triggering requires local access to the DRM/vmwgfx graphics interface or an equivalent local graphics session, but not full administrator privileges. The issue is not network reachable. Impact is at least local denial of service via kernel crash and in the worst case may allow confidentiality and integrity impact or privilege escalation because the bug includes an out-of-bounds write primitive in kernel mapped memory.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 8)	YES	WRITE OOB HARDWARE LINUS KPANIC MEMORY  DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=8
ActionableScoreLower=7

## 1. ActionableScore

* Conservative score: 7
* Paranoid score: 8
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**

## 2. Signal breakdown

* Local unprivileged trigger: +1. A local user with access to the DRM/vmwgfx interface and a configured CRTC can submit a crafted atomic commit using an imported framebuffer.
* Memory corruption, strong corruption primitive: +2. The bug can drive memcpy past the end of source or destination vmaps, including an out-of-bounds write path.
* Reliable kernel crash / strong DoS: +1. Out-of-bounds access from a kernel vmap copy path can realistically crash the kernel.
* Confidentiality impact plausible: +1. The source-side out-of-bounds read may expose adjacent mapped memory depending on layout and copy direction.
* Integrity impact plausible: +1. The destination-side out-of-bounds write can corrupt memory beyond the intended BO mapping.
* Availability impact realistic: +1. Kernel crash is a realistic outcome, not just a warning.
* Weak LPE concern in paranoid score: +1. The primitive is an OOB write in kernel mapped memory, but the exact target and exploitability are not demonstrated, so this is weaker than a proven LPE primitive.

Not counted:

* Remote reachable: +0. This is not network-triggerable.
* Requires admin/root/CAP_SYS_ADMIN: +0. Typical DRM access can be granted to local graphical users and does not necessarily require full root.
* Dirty-Pipe-like ownership/COW violation: +0. The patch shows imported dma-buf copy bounds issues, but not a supported file-backed COW or page-cache ownership bypass.
* Race penalty: +0. This is not a timing race.

## 3. Reachability analysis

The realistic trigger is local access to the VMware graphics DRM device, plus the ability to configure a CRTC and submit an atomic commit involving an imported dma-buf framebuffer. This usually maps to PR:L rather than PR:H, because graphical sessions commonly grant users access to DRM device nodes. Containers reduce exposure unless the DRM device is passed through. The affected path is not a generic Linux default path, but it is relevant in VMware guest environments using vmwgfx and dma-buf framebuffer import.

## 4. Severity interpretation

This is stronger than an ordinary Moderate issue because the patch fixes explicit bounds failures in both bulk and row-by-row copy paths, including unsigned subtraction wrap, multiplication overflow, and missing endpoint validation. The realistic demonstrated impact is local kernel crash or memory corruption. Theoretical privilege escalation is plausible enough for manual review because the bug includes a destination OOB write in kernel mapped memory, but the patch does not prove controlled target selection or a full exploit chain.

## 5. One-sentence report phrase

A bounds validation flaw in vmwgfx external BO copy allows a local DRM user to craft imported framebuffer state that can make memcpy read or write past the end of mapped buffer objects, causing kernel memory corruption and likely DoS with possible privilege escalation requiring manual review.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the patch shows a concrete OOB read/write primitive in a kernel graphics driver copy path reachable from local DRM operations. This should not be auto-closed even if practical exploitation beyond DoS is not yet demonstrated.

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

Patch: drm/vmwgfx: validate external BO copy bounds for both stride paths
Commit: 4e0f669e2951b742239c6fe847fcc406fe78748d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4e0f669e2951b742239c6fe847fcc406fe78748d

Commit description:

vmw_external_bo_copy() trusts caller-supplied offsets, strides, and
heights and operates on imported dma-buf vmaps:

  - The equal-stride memcpy() bound was clamped after subtracting the
    offsets from dst_size and src_size; an offset larger than the BO
    size wraps the unsigned subtraction to a huge value and the
    resulting memcpy() runs off the end of the vmap.  dst_stride *
    height is also a u32 multiplication that can overflow.
  - The non-equal-stride row-by-row path had no bound at all.  The
    loop touches bytes through offset + (height - 1) * stride +
    width_in_bytes, with only a WARN_ON(dst_stride < width_in_bytes),
    and could likewise step past the end of either mapping.

The offsets and strides are derived from STDU/SOU plane state, so a
configured CRTC submitting a crafted atomic commit on an imported
framebuffer can reach this path.

Validate the exact row-copy endpoint against each BO's size up front
using check_mul_overflow() and check_add_overflow().  Use the bulk
memcpy() path only when width_in_bytes covers the whole stride;
otherwise copy one row at a time so partial-row updates near the bottom
of a framebuffer remain valid.  Also reject zero strides and stride <
width_in_bytes, both of which the row-by-row path cannot represent
safely.

Fixes: 50f1199 ("drm/vmwgfx: Fix prime with external buffers")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4.7
Signed-off-by: Zack Rusin <zack.rusin@broadcom.com>
Reviewed-by: Ian Forbes <ian.forbes@broadcom.com>
Link: https://patch.msgid.link/20260505222728.519626-13-zack.rusin@broadcom.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/vmwgfx/vmwgfx_blit.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=4e0f669e2951b742239c6fe847fcc406fe78748d

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

The original Linux kernel CVE announcement for CVE-2026-80700 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80700

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:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7.8

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: 7
  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: MODERATE
KPANIC detected for this report: YES
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).