[CVE-2026-74357][MODERATE 7.0] drm/amdgpu: fix KASAN slab-out-of-bounds in amdgpu_coredump ring dump [ Upstream

[CVE-2026-74357][MODERATE 7.0] drm/amdgpu: fix KASAN slab-out-of-bounds in amdgpu_coredump ring dump [ Upstream

[AL-KERNEL]

CVE: CVE-2026-74357
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: drm/amdgpu: fix KASAN slab-out-of-bounds in amdgpu_coredump ring dump [ Upstream
Commit: efb1dadaeb897b22b9e118d398d0f41e70e9ccca
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=efb1dadaeb897b22b9e118d398d0f41e70e9ccca
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74357
Analysis date: Sat, 15 Aug 2026 16:03:07 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A race in the AMDGPU coredump ring dump can let the copy loop exceed the kcalloc-sized ring array after fence state changes, causing a local slab out-of-bounds write and at least a kernel crash, with possible but unproven privilege escalation risk.

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

The original Linux kernel CVE announcement for CVE-2026-74357 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74357

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-74357	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	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-787;CWE-362;CWE-122;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A slab out-of-bounds write in the AMDGPU coredump path can occur because amdgpu_coredump counts rings with unsignalled fences in one pass and later copies ring dump records in a second pass while fence state can change concurrently. If more rings become eligible during the copy pass than were counted for allocation, idx can exceed ring_count and write past the kcalloc allocated coredump ring array. For the CVSS the PR:L is used because reliable triggering requires a local process able to submit AMDGPU work or otherwise cause GPU reset through DRM access, not full administrator rights. The issue is not network reachable and requires local GPU access plus timing around reset and fence signalling. Impact is at least local denial of service via kernel crash. Because the bug is a race driven slab out-of-bounds write, the paranoid score uses C:H/I:H/A:H as the highest still defensible interpretation for manual review sensitivity.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)  SKIP CVE-2026-74357 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	WRITE KASAN OOB RACE HARDWARE DEBUGFS TEST  INCREASED_TO_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. A local user with access to AMDGPU DRM interfaces may submit GPU work and potentially trigger timeout or reset paths.
* Constrained kernel buffer overwrite: +1. The bug is a confirmed slab out-of-bounds write, but the written field appears limited and kernel-derived rather than an attacker-chosen arbitrary payload.
* Reliable kernel crash / strong DoS: +1. KASAN shows a concrete slab-out-of-bounds write during the reset coredump path.
* Hard or unreliable race / special timing required: -1. The failure depends on fence signalling timing between the count pass and copy pass.

Conservative total: 3

Paranoid additional interpretation:

* Memory corruption, strong corruption primitive: +2 instead of constrained +1. The primitive is a real slab OOB write in kernel heap memory.
* Weak LPE concern: +1. Local privilege escalation is not demonstrated, but a race-driven slab OOB write deserves manual review for adjacent-object corruption potential.
* Integrity impact plausible: +1. Heap metadata or adjacent kernel object corruption could theoretically affect integrity, though no controlled target is shown.
* No confidentiality impact counted. No read-back or information leak path is shown.
* No remote/network signal. This is not network reachable.

Paranoid total after race and constraint penalties: 5

## 3. Reachability analysis

The bug is locally reachable on systems using AMDGPU where a user or process can access the DRM/GPU interface and provoke GPU work that results in timeout, reset, and coredump generation. In typical desktop or compute deployments, render node access may be granted to non-root users through group membership or device ACLs, so PR:L is a reasonable practical assumption.

Containers only matter if `/dev/dri` or the AMDGPU device is passed through. Without GPU device access, the path is not reachable from a container. The bug is not remotely reachable by packet traffic or network input. Triggering is realistic for GPU stress or malformed command submission workloads, but the race is non-deterministic and depends on fence timing during reset.

Call-site confidence: high. The patch, affected function, allocation, copy loop, KASAN trace, and reset call path are all present in the input.

## 4. Severity interpretation

This is more than an ordinary Moderate because it is confirmed kernel heap memory corruption, not just a warning or resource leak. Realistic exploitation evidence points primarily to local DoS through GPU reset and crash conditions. Practical privilege escalation is not demonstrated because the overwrite appears constrained and timing-dependent, with no shown attacker-controlled target or payload.

The conservative score therefore stays borderline/manual-review. The paranoid score reaches Actionable Moderate because slab OOB writes in local kernel driver paths have historically been under-triaged when treated as DoS only.

## 5. One-sentence report phrase

A race in the AMDGPU coredump ring dump can let the copy loop exceed the kcalloc-sized ring array after fence state changes, causing a local slab out-of-bounds write and at least a kernel crash, with possible but unproven privilege escalation risk.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: confirmed slab out-of-bounds write in kernel heap memory, local user reachability through GPU access, and possible adjacent-object corruption despite constrained payload and race timing.

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

Patch: drm/amdgpu: fix KASAN slab-out-of-bounds in amdgpu_coredump ring dump [ Upstream
Commit: efb1dadaeb897b22b9e118d398d0f41e70e9ccca
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=efb1dadaeb897b22b9e118d398d0f41e70e9ccca

Changed files:
  drivers/gpu/drm/amd/amdgpu/amdgpu_dev_coredump.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=efb1dadaeb897b22b9e118d398d0f41e70e9ccca

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

The original Linux kernel CVE announcement for CVE-2026-74357 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74357

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: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: 3
  Paranoid ActionableScore: 5

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 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).