[CVE-2026-68257][MODERATE 7.0] drm/amdkfd: fix 32-bit overflow in CWSR total size calculation

[CVE-2026-68257][MODERATE 7.0] drm/amdkfd: fix 32-bit overflow in CWSR total size calculation

[AL-KERNEL]

CVE: CVE-2026-68257
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: drm/amdkfd: fix 32-bit overflow in CWSR total size calculation
Commit: b88ffe6593607364a8c06a48c6f29e55437cdf8e
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b88ffe6593607364a8c06a48c6f29e55437cdf8e
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68257
Analysis date: Mon, 10 Aug 2026 19:23:05 -0400
ActionableScore: 8
ActionableScore lower bound: 6
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A 32-bit overflow in AMD KFD CWSR size calculation can produce an undersized BO/SVM save area that firmware later overruns, creating a local memory corruption and DoS risk with plausible privilege escalation concerns on systems exposing KFD access to non-root users.

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

The original Linux kernel CVE announcement for CVE-2026-68257 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68257

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-2026-68257	MODERATE	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:H/I:H/A:H';CWE-190;CWE-680;*CWE-787;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A 32-bit integer overflow in the AMD KFD CWSR size calculation can make total_cwsr_size wrap before it is used as a BO/SVM allocation or pinning size. A local process with access to AMD KFD queue creation can request large ctx_save_restore_area_size values which are combined with debug memory size and multiplied by the XCC count, producing an undersized CWSR save area. Firmware may later write the real CWSR state beyond that undersized area, so the primitive is an out of bounds write candidate rather than a simple warning or resource leak. For the CVSS the PR:L is used because reliable triggering requires local code execution with access to the KFD device interface, not full administrative privileges. The issue is not directly network reachable. Impact is at least local denial of service via GPU or kernel memory corruption, and in the worst case may allow confidentiality or integrity impact including privilege escalation depending on memory placement and GPU memory access semantics.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 8)  SKIP CVE-2026-68257 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	SIMPLEFIX HARDWARE KPANIC MEMORY  KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7 DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP	-	-	checked

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

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 scoring:

* Local unprivileged trigger: +1
  A local process with access to AMD KFD queue creation can influence `ctx_save_restore_area_size`. This normally does not require full host root, but does require access to `/dev/kfd` or GPU device permissions such as render/video group membership.

* Firmware-mediated external influence: +1
  The actual overwrite is performed later by GPU firmware using an undersized CWSR save area.

* Constrained kernel/device buffer overwrite: +1
  The integer overflow can create an undersized BO/SVM backing area, and firmware may write past it. The overwrite is real, but payload and target control are not fully demonstrated.

* Memory layout invariant restoration: +1
  The patch restores consistency between the calculated CWSR size and the BO/SVM buffer size by using `u64` and checked multiplication.

* Reliable kernel crash / strong DoS: +1
  A firmware overrun of a too-small save area can realistically lead to GPU reset, driver failure, or kernel memory corruption with crash potential.

* Privileged kernel/device-management memory corruption path: +1
  The corruption occurs in a trusted GPU driver and firmware interaction path, involving BO/SVM memory management.

* Weak LPE concern: +1
  Privilege escalation is not proven, but an undersized allocation followed by firmware OOB write is a credible memory-corruption sink that should not be auto-closed as DoS-only.

* Corruption primitive constrained or no proven attacker-controlled payload/target: -1
  The patch does not show an arbitrary write primitive, attacker-selected adjacent object, or controlled reclaim strategy.

Conservative total: 6

Paranoid scoring:

* Local unprivileged trigger: +1
* Firmware-mediated external influence: +1
* Memory corruption, strong corruption primitive: +2
  In the paranoid interpretation, the firmware overrun of an undersized BO/SVM CWSR area is treated as an OOB write candidate.
* Memory layout invariant restoration: +1
* Reliable kernel crash / strong DoS: +1
* Privileged kernel/device-management memory corruption path: +1
* Privilege escalation plausible: +2
  If BO/SVM placement or adjacent memory can be influenced, the firmware overrun could corrupt security-relevant GPU or kernel-managed memory.
* Corruption primitive constrained or no proven attacker-controlled payload/target: -1

Paranoid total: 8

## 3. Reachability analysis

The bug is locally reachable through AMD KFD queue setup paths. A realistic attacker needs local code execution and access to the KFD GPU device interface. This is often available to users in GPU or compute environments through `/dev/kfd` and render nodes, but it is not universally available to every local user.

This is not network reachable. Containers or sandboxed workloads may matter if GPU devices are passed through into the container, because container root or a service account with GPU access should not be treated as equivalent to full host root.

The affected path is hardware and deployment dependent. It requires AMD GPU KFD support and relevant CWSR behavior, but the interface is ordinary for ROCm or GPU compute systems rather than a rare debug-only path.

Call-site confidence: high. The patch shows both acquire and release paths where `total_cwsr_size` is used for BO/SVM buffer accounting, and the commit explicitly states that firmware later overruns the undersized CWSR area.

## 4. Severity interpretation

This behaves above an ordinary Moderate issue because the commit describes an integer overflow leading to an undersized allocation and a later firmware overrun. That is a concrete memory corruption candidate, not just a validation cleanup or resource leak.

Realistic exploitation evidence is incomplete. The patch does not demonstrate attacker-controlled overwrite contents, adjacent object control, or a working privilege escalation chain. Therefore the conservative result is Actionable Moderate.

The paranoid result reaches Strong Important candidate because the primitive is an OOB write in a trusted GPU firmware and kernel driver memory-management path, and local GPU access is commonly delegated to non-root users in compute environments.

## 5. One-sentence report phrase

A 32-bit overflow in AMD KFD CWSR size calculation can produce an undersized BO/SVM save area that firmware later overruns, creating a local memory corruption and DoS risk with plausible privilege escalation concerns on systems exposing KFD access to non-root users.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

This should be manually reviewed because the patch explicitly describes an undersized allocation followed by firmware overrun, which is a concrete OOB write candidate in a privileged GPU memory-management path.

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

Patch: drm/amdkfd: fix 32-bit overflow in CWSR total size calculation
Commit: b88ffe6593607364a8c06a48c6f29e55437cdf8e
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b88ffe6593607364a8c06a48c6f29e55437cdf8e

Commit description:

total_cwsr_size was computed in 32-bit before being used as a BO/SVM
allocation size.
With large ctx_save_restore_area_size and debug_memory_size
multiplied by the XCC count, the product can wrap,
yielding an undersized CWSR save area that firmware later overruns.

Promote total_cwsr_size to u64 and use check_add_overflow()/
check_mul_overflow() in both kfd_queue_acquire_buffers() and
kfd_queue_release_buffers().

Signed-off-by: Yongqiang Sun <Yongqiang.Sun@amd.com>
Reviewed-by: Philip Yang <philip.yang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 319f7e1 )
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/amd/amdkfd/kfd_queue.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=b88ffe6593607364a8c06a48c6f29e55437cdf8e

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

The original Linux kernel CVE announcement for CVE-2026-68257 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68257

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: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: 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).