[CVE-2026-89807][MODERATE REGULAR] drm/amdkfd: guard against NULL restore_mqd in CRIU queue restore

[CVE-2026-89807][MODERATE REGULAR] drm/amdkfd: guard against NULL restore_mqd in CRIU queue restore

[AL-KERNEL]

CVE: CVE-2026-89807
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: drm/amdkfd: guard against NULL restore_mqd in CRIU queue restore
Commit: 19c73848493ab58e39649700da6de11710a36de1
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=19c73848493ab58e39649700da6de11710a36de1
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89807
Analysis date: Wed, 16 Sep 2026 13:46:32 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
A local user with CAP_CHECKPOINT_RESTORE and access to AMD KFD CRIU restore can trigger a NULL restore_mqd callback dereference for unsupported queue restore paths, causing a kernel panic DoS.

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

The original Linux kernel CVE announcement for CVE-2026-89807 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89807

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: NO

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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

CVE-2026-89807	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-89807 CHECK WITH IMPACT FROM ORIG NN MODERATE	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-754;CWE-703;BEST CVSS score: '5.5';DESCR 'A NULL function pointer dereference in AMD KFD CRIU queue restore can occur because create_queue_cpsch and create_queue_nocpsch call restore_mqd when qd is present without checking whether the callback is implemented. A local attacker with access to KFD_IOC_CRIU_OP_RESTORE can provide a crafted queue restore object for a queue type or GPU where restore_mqd is NULL, causing a kernel crash. For the CVSS the PR:L is used because CAP_CHECKPOINT_RESTORE or an equivalent delegated restore capability is required, but this is a limited local privilege rather than full administrative control in many deployments. The issue is not network reachable and requires local code execution plus access to the AMD KFD device. Impact is denial of service via kernel panic. No UAF, OOB access, arbitrary write, or information disclosure primitive is indicated by the code change, so confidentiality and integrity are not increased in the paranoid score.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)  SKIP CVE-2026-89807 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	DANGER NULLPTR SIMPLEFIX HARDWARE  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH	-	-	checked

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

ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES

## 1. ActionableScore

* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 1
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate**::

No floor or cap was applied.

## 2. Signal breakdown

Positive signals:

* +1 Weak / indirect invalid callback target: `restore_mqd` is a function pointer that may be NULL and is called without a guard.
* +1 Reliable kernel crash / strong DoS: supplied context states that `KFD_IOC_CRIU_OP_RESTORE` with crafted queue restore data can trigger a NULL pointer dereference and panic the machine.

Negative / limiting signals:

* -1 Reduced / delegated privilege requirement: triggering requires `CAP_CHECKPOINT_RESTORE` or equivalent restore capability, which is below full host-admin in many models but still not ordinary unprivileged access.

Important non-awarded signals:

* RealUAF not awarded: no use-after-free, stale reference, double release, or refcount lifetime mutation is shown.
* CLASS_A not awarded: no controlled reclaim, arbitrary write, callback hijack via attacker-controlled pointer, or LPE chain is established.
* Confidentiality and integrity not awarded: no information disclosure or unauthorized state modification primitive is shown.
* Extra availability not awarded: the same kernel panic is already counted once.
* Remote reachability not awarded: this is a local DRM/KFD ioctl path, not packet-triggered.
* Structured stale-object leverage not awarded: there is no stale object reuse path.
* Concrete repeated release/refcount signal not applicable: no first release, surviving exact reference, and second lifetime mutation are present.

## 3. Reachability analysis

The trigger is local through the AMD KFD CRIU restore ioctl path, specifically `KFD_IOC_CRIU_OP_RESTORE`, with a crafted queue restore object. The supplied context states that the attacker needs `CAP_CHECKPOINT_RESTORE`.

This is not host-admin-equivalent by itself, so `HostAdminRequired=NO`. However, it is still a privileged local capability, not ordinary unprivileged reachability. The complete namespace behavior is not established from the supplied patch, because the analysis does not prove that the whole KFD device access and CRIU restore operation is available inside attacker-created namespaces. Therefore `NamespaceScopedPrivilege=UNKNOWN`.

The issue also requires a relevant AMD KFD environment and a queue type or GPU generation where `restore_mqd` is not implemented, such as the GFX12-related context mentioned in the input. This is hardware dependent but not enough to apply a rare-hardware penalty by itself. No race or special timing is required.

## 4. Primitive and severity interpretation

The exact primitive is a NULL function pointer dereference: `create_queue_cpsch()` and `create_queue_nocpsch()` call `mqd_mgr->restore_mqd()` when `qd != NULL` without checking whether the callback exists.

This is not an active structured UAF and not fixed stale storage. It is a direct invalid callback invocation where the expected consequence is an immediate kernel fault or panic. The demonstrated consequence is local denial of service. Stronger consequences such as privilege escalation, arbitrary kernel read/write, controlled function pointer redirection, or information disclosure are not supported by the patch.

Primitive classification is `CLASS_C` because the demonstrated behavior is crash/DoS from invalid state, without an independently useful corruption primitive. `ImportantCandidate=NO` because the patch does not establish unresolved memory corruption or a meaningful post-lifetime exploitation primitive. `AutoDowngradeAllowed=YES` because the issue is constrained to a local capability-gated NULL dereference DoS with no UAF, no repeated lifetime mutation, and no security-boundary bypass.

Operationally this is an ordinary Moderate-style kernel DoS issue, with manual review useful mainly to confirm exact product exposure, capability policy, and affected AMD GPU/KFD configurations.

## 5. One-sentence report phrase

A local user with CAP_CHECKPOINT_RESTORE and access to AMD KFD CRIU restore can trigger a NULL restore_mqd callback dereference for unsupported queue restore paths, causing a kernel panic DoS.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: the primitive is crash-only, but review is useful to confirm whether `CAP_CHECKPOINT_RESTORE`, `/dev/kfd` access, and the affected GPU queue type are reachable in the evaluated product.

## 7. Call-site confidence

Call-site confidence: high

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

Patch: drm/amdkfd: guard against NULL restore_mqd in CRIU queue restore
Commit: 19c73848493ab58e39649700da6de11710a36de1
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=19c73848493ab58e39649700da6de11710a36de1

Commit description:

Both create_queue_cpsch() and create_queue_nocpsch() unconditionally
call mqd_mgr->restore_mqd() when a CRIU restore is in progress
(qd != NULL), with no NULL guard. On any system where restore_mqd is
not implemented for the given queue type, a user holding
CAP_CHECKPOINT_RESTORE can trigger a kernel NULL pointer dereference
and panic the machine by issuing KFD_IOC_CRIU_OP_RESTORE with a
crafted queue restore object. Note that checkpoint_mqd is likewise
unimplemented on GFX12, so no legitimate CRIU image can reach this
path — only a hand-crafted restore payload.

Add a NULL guard for restore_mqd immediately after mqd_mgr is
resolved, unwinding via the existing error labels and returning
-EOPNOTSUPP if the callback is not implemented. This mirrors the
existing checkpoint_mqd guard in checkpoint_mqd().

Fixes: 48f0bdf ("drm/amdkfd: Added MQD manager files for GFX12.")
Cc: stable@vger.kernel.org
Signed-off-by: Vladimir Marioukhine <Vladimir.Marioukhine@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.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=19c73848493ab58e39649700da6de11710a36de1

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

The original Linux kernel CVE announcement for CVE-2026-89807 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89807

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: unknown
  Paranoid ActionableScore: 1

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).