[CVE-2026-63882][MODERATE REGULAR] drm/amdkfd: fix NULL pointer bug in svm_range_set_attr

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

CVE: CVE-2026-63882
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: drm/amdkfd: fix NULL pointer bug in svm_range_set_attr
Commit: e4dcb5d6360319609bc5b05fb40e98b0af6bc674
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e4dcb5d6360319609bc5b05fb40e98b0af6bc674
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63882
Analysis date: Sun, 19 Jul 2026 21:13:15 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Borderline, manual review recommended. Not an Important candidate
Manual review required: YES

Summary:
A local NULL pointer dereference in the AMD KFD SVM ioctl path allows a user with access to the KFD GPU device node to crash the kernel by calling the SVM ioctl before acquiring the VM context.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-63882 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63882

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 REGULAR
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-2026-63882	MODERATE	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:L/UI:N/S:U/C:N/I:N/A:H';**CWE-476;*CWE-20;CWE-754;BEST CVSS score: '5.5';DESCR 'A local NULL-pointer dereference in the AMD KFD SVM ioctl path can occur because svm_range_set_attr uses process_info before verifying that it was initialized. A local user with access to the KFD device can trigger this by calling the SVM ioctl without first acquiring the VM context through kfd_ioctl_acquire_vm. For the CVSS the PR:L is used because reliable triggering requires local code execution and access to the GPU device node, but not full administrative privileges. The issue is not network reachable. Impact is denial of service via kernel oops or crash, with no supported evidence of memory corruption, information disclosure, or privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended. Not an Important candidate (with actual score 3)  SKIP CVE-2026-63882 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	SIMPLEFIX HARDWARE  INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=3
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 3
* Final recommended bucket: **Borderline, manual review recommended. Not an Important candidate**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. A local user with access to the AMD KFD GPU device node can call `kfd_ioctl_svm` without first calling `kfd_ioctl_acquire_vm`.
* Reliable kernel crash / strong DoS: +1. `process_info` is dereferenced via `mutex_lock(&process_info->lock)` when it can be NULL, which can cause a kernel Oops or crash.

Paranoid additional signal:

* Availability impact realistic: +1. If the affected device node is accessible to local users and the system uses panic-on-oops or similar policy, this can become a practical host-wide DoS.

Signals not awarded:

* No generic memory corruption. This is a NULL pointer dereference, not UAF, OOB write, double-free, type confusion, or refcount misuse.
* No privilege escalation signal. The patch does not show attacker-controlled reclaim, object replacement, write primitive, callback control, or type confusion.
* No confidentiality or integrity impact. There is no read-back, information leak, or corruption primitive.
* No high-control GPU API bonus. The patch shows invalid call ordering and missing validation, not attacker control over memory layout, lifetime, refcounts, DMA mappings, or page ownership.

## 3. Reachability analysis

The bug is locally reachable through the AMD KFD SVM ioctl path. Reliable triggering requires local code execution and access to the relevant GPU device node, commonly through `render` or `video` group permissions depending on the distribution and deployment.

Namespaces and containers may matter if GPU device nodes are passed into containers. In such setups, a container user with access to the KFD device could potentially trigger the same host kernel bug, but this still depends on device-node delegation.

The path is not network reachable. It requires an AMD GPU/KFD environment with SVM functionality exposed, so exposure is narrower than a core kernel syscall path but realistic on GPU compute or ROCm-style systems.

Call-site confidence: high. The patch shows the immediate NULL check added directly before the dereference site.

## 4. Severity interpretation

This behaves like an ordinary Moderate local DoS, with a borderline manual-review reason due to possible user-accessible GPU device nodes and panic-on-oops policy.

Theoretical impact beyond DoS is weak. The bug class is NULL pointer dereference and the patch does not support a memory-corruption or privilege-escalation primitive. Realistic exploitation evidence supports local kernel crash only.

## 5. One-sentence report phrase

A local NULL pointer dereference in the AMD KFD SVM ioctl path allows a user with access to the KFD GPU device node to crash the kernel by calling the SVM ioctl before acquiring the VM context.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED.

YES REQUIRES MANUAL CHECK because practical risk depends on GPU device-node exposure, container passthrough, and panic-on-oops policy, although the bug itself appears to be NULL dereference DoS only.

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

Patch: drm/amdkfd: fix NULL pointer bug in svm_range_set_attr
Commit: e4dcb5d6360319609bc5b05fb40e98b0af6bc674
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e4dcb5d6360319609bc5b05fb40e98b0af6bc674

Commit description:

The process_info could be NULL if user doesn't call kfd_ioctl_acquire_vm
before calling kfd_ioctl_svm.

Signed-off-by: Eric Huang <jinhuieric.huang@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 83a26c8 )
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/amd/amdkfd/kfd_svm.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=e4dcb5d6360319609bc5b05fb40e98b0af6bc674

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

The original Linux kernel CVE announcement for CVE-2026-63882 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63882

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: Not available
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.5

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: 2
  Paranoid ActionableScore: 3

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 REGULAR

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).