[CVE-2026-68259][MODERATE REGULAR] drm/amdkfd: Check bounds in allocate_event_notification_slot

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

CVE: CVE-2026-68259
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: drm/amdkfd: Check bounds in allocate_event_notification_slot
Commit: 85eedff5f0c4aba5a66bc37a1bd6bcecd0d77b53
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=85eedff5f0c4aba5a66bc37a1bd6bcecd0d77b53
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68259
Analysis date: Mon, 10 Aug 2026 13:20:23 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Borderline, manual review recommended
Manual review required: YES

Summary:
A missing upper bound check in amdkfd allocate_event_notification_slot lets a local KFD user request a restored event id outside KFD_SIGNAL_EVENT_LIMIT, creating invalid event state with possible local DoS impact but no demonstrated strong memory corruption primitive.

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

The original Linux kernel CVE announcement for CVE-2026-68259 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68259

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-2026-68259	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:L/I:L/A:H';CWE-129;*CWE-20;CWE-754;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '6.6';DESCR 'A missing upper bound check in amdkfd allocate_event_notification_slot allowed a restored event id to be allocated outside the valid KFD_SIGNAL_EVENT_LIMIT range. A local process with access to the AMD KFD interface could provide an invalid restore id through the event restore path used by CRIU, creating an event state that violates the expected signal event id bounds. For the CVSS the PR:L is used because triggering requires local code execution and access to the KFD device interface, commonly through /dev/kfd or a GPU access group. The issue is not network reachable. The base impact is limited because the patch only proves improper input validation and does not by itself show a concrete arbitrary read or write primitive. The paranoid impact keeps C:L/I:L/A:H because the bug is a user controlled bounds violation in a kernel GPU driver and the invalid id may later interact with signal event slot assumptions.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 3)  SKIP CVE-2026-68259 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	OOB SIMPLEFIX HARDWARE  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**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. A local process with access to the AMD KFD device interface may be able to provide the restored event id.
* Memory corruption, weak or indirect corruption candidate: +1. The bug is an unchecked user influenced object id that can exceed KFD_SIGNAL_EVENT_LIMIT, but the patch does not show a concrete OOB read, OOB write, UAF, double free, or controlled overwrite.

Paranoid additional signal:

* Availability impact plausible: +1. An invalid event id outside the expected signal event range may later interact with missing signal mode mappings or invalid event bookkeeping, so a local driver DoS is plausible, but not demonstrated.

Not awarded:

* No remote reachability.
* No strong generic memory corruption primitive.
* No strong LPE plausibility.
* No confidentiality or integrity impact in the conservative score.
* No high-control device API bonus, because the patch only shows object id validation and not attacker control over memory layout, lifetime, DMA mappings, callbacks, or refcounts.

## 3. Reachability analysis

The likely trigger is local access to the AMD KFD interface, commonly through /dev/kfd or a GPU access group. This is not network reachable. It does not require full host root if the local user is allowed to use AMD GPU compute interfaces, so the practical privilege interpretation is closer to local user access than PR:H.

The affected path is narrower than ordinary event creation because restore_id is described as used by CRIU. That makes exploitation more configuration and workflow dependent, but not rare enough to dismiss if untrusted local users can access KFD. Call-site confidence is medium-low because the patch shows the validation site but not downstream consumers of out-of-range event ids.

## 4. Severity interpretation

This behaves more like a borderline Moderate validation bug than an Important-class vulnerability based on the provided patch. The theoretical concern is that an out-of-range event id in a kernel GPU driver could later be used as an invalid index or invalid event state. The realistic evidence is weaker: the diff only proves missing upper-bound validation and does not demonstrate memory corruption, privilege escalation, or a reliable crash.

The conservative score should stay low. The paranoid score is suitable for manual review because the bug is user controlled and located in a kernel driver event-management path.

## 5. One-sentence report phrase

A missing upper bound check in amdkfd allocate_event_notification_slot lets a local KFD user request a restored event id outside KFD_SIGNAL_EVENT_LIMIT, creating invalid event state with possible local DoS impact but no demonstrated strong memory corruption primitive.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED. The issue should not be treated as Important from the patch alone, but downstream uses of event ids should be checked for array indexing, signal slot lookup, mapping access, or cleanup paths that assume the id is below KFD_SIGNAL_EVENT_LIMIT.

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

Patch: drm/amdkfd: Check bounds in allocate_event_notification_slot
Commit: 85eedff5f0c4aba5a66bc37a1bd6bcecd0d77b53
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=85eedff5f0c4aba5a66bc37a1bd6bcecd0d77b53

Commit description:

The valid event ids go from 0 to KFD_SIGNAL_EVENT_LIMIT

allocate_event_notification_slot has an option to specify
an event id to allocate at, used by CRIU. We weren't checking
the bounds on that value.

Check them.

v2: Lower bounds check is unecessary because of idr_alloc
already rejecting negative numbers. Upper bounds check should
be KFD_SIGNAL_EVENT_LIMIT since the signal mode mappings might
not yet exist

Signed-off-by: David Francis <David.Francis@amd.com>
Reviewed-by: David Yat Sin <david.yatsin@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 6853f1f )
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/amd/amdkfd/kfd_events.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=85eedff5f0c4aba5a66bc37a1bd6bcecd0d77b53

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

The original Linux kernel CVE announcement for CVE-2026-68259 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68259

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:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 6.6

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).