[CVE-2026-74448][LOW] drm/amdkfd: fix QID bit leak in pqm_create_queue()

[CVE-2026-74448][LOW] drm/amdkfd: fix QID bit leak in pqm_create_queue()

[AL-KERNEL]

CVE: CVE-2026-74448
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: drm/amdkfd: fix QID bit leak in pqm_create_queue()
Commit: 8924e2594a15bdbd07f8696770864366d787ab70
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8924e2594a15bdbd07f8696770864366d787ab70
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74448
Analysis date: Sat, 15 Aug 2026 12:01:05 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like. Autoclose candidate
Manual review required: YES

Summary:
A local QID slot leak in AMD KFD queue creation can occur when MES is enabled and process context allocation fails, allowing repeated failures to exhaust GPU queue slots and cause a local denial of service.

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

The original Linux kernel CVE announcement for CVE-2026-74448 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74448

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: LOW
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-2026-74448	LOW	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:N/I:N/A:H';*CWE-772;**CWE-400;CWE-404;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'A QID slot leak in drm amdkfd can occur when MES is enabled and amdgpu_amdkfd_alloc_kernel_mem fails during the first queue creation for a process. The failing path returned directly and skipped the cleanup that clears the reserved bit in pqm queue_slot_bitmap, so repeated failures can leave queue identifiers permanently marked as used and may exhaust queue slots. For the CVSS the PR:L is used for the paranoid score because a local user or process with access to the KFD GPU interface may request queues, but reliable triggering still depends on MES being enabled and on hitting the allocation failure path. The issue is not network reachable and is a local GPU resource exhaustion problem. Impact is denial of service for queue creation or GPU compute availability, with no evidence of memory corruption, information disclosure, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like. Autoclose candidate (with actual score 2)  SKIP CVE-2026-74448 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	SIMPLEFIX LEAK ERRORPATH HARDWARE 	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=2
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like. Autoclose candidate**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. A local process with access to the AMD KFD GPU interface may be able to request queue creation.
* Availability impact realistic: +1. Repeated QID bit leaks can eventually exhaust queue slots and prevent further queue creation.
* Hard or unreliable condition: -1. Triggering depends on MES being enabled and on `amdgpu_amdkfd_alloc_kernel_mem()` failing during the first queue creation path.

Paranoid interpretation:

* Score can be raised to 2 if repeated failure conditions are considered practically reproducible on affected systems and GPU queue exhaustion affects compute availability for other workloads.
* No memory corruption, UAF, OOB write, refcount abuse, stale callback, arbitrary write, or privilege escalation primitive is shown by the patch.

## 3. Reachability analysis

The bug is local and requires access to the AMD KFD device interface. It is not network reachable. In typical deployments, access may be limited to users in GPU related device groups or container workloads with GPU passthrough. Namespaces do not automatically make this reachable unless the KFD device is exposed into the namespace or container. The path also depends on MES being enabled and on a kernel memory allocation failure occurring at a specific queue creation stage, so reliable triggering is not guaranteed.

Call-site confidence: high. The patch and commit message directly identify `pqm_create_queue()` and the missed cleanup of `pqm->queue_slot_bitmap`.

## 4. Severity interpretation

This behaves like a constrained local resource leak rather than an Important-class vulnerability. The realistic impact is denial of service against AMD KFD queue allocation or GPU compute availability. There is no evidence of confidentiality impact, integrity impact, kernel memory corruption, or privilege escalation. The paranoid score remains low because the bug leaks a bookkeeping bit rather than corrupting attacker-controlled kernel memory.

## 5. One-sentence report phrase

A local QID slot leak in AMD KFD queue creation can occur when MES is enabled and process context allocation fails, allowing repeated failures to exhaust GPU queue slots and cause a local denial of service.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED. NO MANUAL CHECK REQUIRED COULD BE AUTOCLOSED.

Reason: this is a constrained resource leak in an error path with no demonstrated memory corruption or privilege escalation primitive, and the practical trigger depends on a specific allocation failure condition.

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

Patch: drm/amdkfd: fix QID bit leak in pqm_create_queue()
Commit: 8924e2594a15bdbd07f8696770864366d787ab70
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8924e2594a15bdbd07f8696770864366d787ab70

Commit description:

When MES is enabled and amdgpu_amdkfd_alloc_kernel_mem() fails during
the first queue creation for a process, pqm_create_queue() returns
early via 'return retval' without going through the err_create_queue
cleanup label.

This means clear_bit(*qid, pqm->queue_slot_bitmap) is never called,
leaving the reserved QID bit permanently set in queue_slot_bitmap.
Over time this leaks QID slots, potentially exhausting all available
queue slots.

Fix this by replacing 'return retval' with 'goto err_allocate_pqn'
so that clear_bit() is always called on the error path without
touching the uninitialized pqn pointer.

AILIKFD-813

Reported-by: Deucher, Alexander <alexander.deucher@amd.com>
Signed-off-by: Vladimir Marioukhine <Vladimir.Marioukhine@amd.com>
Reviewed-by: Kent Russell <kent.russell@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit a107f74 )
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/amd/amdkfd/kfd_process_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=8924e2594a15bdbd07f8696770864366d787ab70

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

The original Linux kernel CVE announcement for CVE-2026-74448 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74448

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:H/PR:L/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: 1
  Paranoid ActionableScore: 2

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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).