[CVE-2026-53329][IMPORTANT] drm/amd/display: Use krealloc_array() in dal_vector_reserve()

[CVE-2026-53329][IMPORTANT] drm/amd/display: Use krealloc_array() in dal_vector_reserve()

[AL-KERNEL]

CVE: CVE-2026-53329
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: drm/amd/display: Use krealloc_array() in dal_vector_reserve()
Commit: 31180638a33acad12c863132704a76536fb66211
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=31180638a33acad12c863132704a76536fb66211
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53329
Analysis date: Wed, 01 Jul 2026 10:12:29 -0400
ActionableScore: 7
ActionableScore lower bound: 5
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
An integer overflow in `drm/amd/display` `dal_vector_reserve()` can cause an undersized allocation and subsequent kernel heap overflow during vector appends, making this a local memory-corruption issue with DoS impact and plausible LPE risk.

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

The original Linux kernel CVE announcement for CVE-2026-53329 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53329

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: IMPORTANT
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
======================================================================

CVE-2026-53329	IMPORTANT	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:H/I:H/A:H';CWE-190;CWE-131;CWE-122;*CWE-787;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'An integer overflow in drm/amd/display dal_vector_reserve can make capacity multiplied by struct_size wrap to a smaller allocation size. Subsequent vector appends may then write past the end of the reallocated heap buffer, creating a kernel heap overflow condition. For the CVSS the PR:L is used because reliable triggering is expected to require local access to DRM display control paths or an equivalent local process context, not remote network access. The issue is not network reachable in the normal model and depends on AMD display driver exposure and controllable display or modeset state. Impact is at least local denial of service via memory corruption and in the paranoid case may allow confidentiality or integrity impact including privilege escalation, so it should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7)  SKIP CVE-2026-53329  SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	SIMPLEFIX HARDWARE  KPANIC INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7	-	-	checked

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

ActionableScore=7
ActionableScoreLower=5

## 1. ActionableScore

* Conservative score: 5
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. Likely reachable by a local process with access to DRM display control paths, for example via `/dev/dri/card*` permissions, seat access, or equivalent local graphics stack context.
* Memory corruption, strong corruption primitive: +2. The commit explicitly states that `capacity * vector->struct_size` can wrap and cause an undersized `krealloc()`, followed by heap overflows on later vector appends.
* Weak LPE concern: +1. Kernel heap overflow makes privilege escalation plausible, but the patch does not show attacker-controlled target selection, reclaim, object replacement, or a demonstrated write primitive.
* Reliable kernel crash / strong DoS: +1. A kernel heap overflow in the AMD display driver can realistically crash or destabilize the kernel.
* Broad/default/common subsystem on affected hardware: +1. AMDGPU display code is commonly enabled and loaded by default on systems with affected AMD graphics hardware.
* Hard or configuration-dependent triggering: -1. Reaching a wrapping `capacity` likely requires a specific display/vector growth path and high-control modeset or display-state conditions.

Paranoid additions:

* Privilege escalation plausible: upgraded from weak +1 to strong +2 in the paranoid score because the patch explicitly describes a kernel heap overflow, a bug class that historically warrants manual LPE review.
* Integrity impact plausible: +1. In the paranoid interpretation, an out-of-bounds heap write may corrupt adjacent kernel objects even though no concrete exploit primitive is shown.

Not counted:

* No remote reachable signal. This is not a network protocol or packet-processing path.
* No firmware-mediated external influence signal based on the provided patch.
* No Dirty-Pipe-like or page-cache corruption signal.
* No confidentiality impact in the conservative score because no information leak or read-back primitive is described.

## 3. Reachability analysis

The realistic trigger is local, through AMD DRM display functionality. The likely attacker model is a local user or process that can access DRM display control interfaces, not a remote network attacker. Namespaces and containers may matter if DRM device nodes are passed through to a container or if a graphical/session service exposes modeset control on behalf of a user. In ordinary deployments, `/dev/dri/card*` access is often limited to local seat users, the `video` group, display managers, or privileged graphics services, so PR:L is more appropriate than PR:N.

The affected path is hardware-dependent but not rare on AMD GPU systems. The main uncertainty is call-site controllability: the patch shows the vulnerable allocator helper and the commit states that later vector appends can overflow, but the exact external input path that drives `capacity` to a wrapping value is not included. Call-site confidence: medium.

## 4. Severity interpretation

This should not be treated as an ordinary Moderate auto-close candidate. The conservative interpretation is Actionable Moderate because the patch directly fixes an integer-overflow-to-heap-overflow condition in kernel space. The paranoid interpretation is a Strong Important candidate because kernel heap overflow can plausibly become LPE if the vector contents, append pattern, or neighboring heap layout are attacker-influenceable.

Theoretical memory corruption potential is strong and explicitly supported by the commit. Realistic exploitation evidence is incomplete because no concrete reclaim, target object corruption, or working LPE path is shown.

## 5. One-sentence report phrase

An integer overflow in `drm/amd/display` `dal_vector_reserve()` can cause an undersized allocation and subsequent kernel heap overflow during vector appends, making this a local memory-corruption issue with DoS impact and plausible LPE risk.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

The patch explicitly describes a kernel heap overflow, and even though triggerability and exploit control are not fully demonstrated, this bug class should be manually reviewed for local privilege escalation potential.

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

Patch: drm/amd/display: Use krealloc_array() in dal_vector_reserve()
Commit: 31180638a33acad12c863132704a76536fb66211
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=31180638a33acad12c863132704a76536fb66211

Commit description:

[Why & How]
dal_vector_reserve() computes the allocation size as
"capacity * vector->struct_size" using uint32_t arithmetic, which can
silently wrap to a small value on overflow. This would cause krealloc to
return a smaller buffer than expected, leading to heap overflows on
subsequent vector appends.

Replace krealloc() with krealloc_array() which performs an internal
overflow check and returns NULL on wrap, preventing the issue.

Fixes: 2004f45 ("drm/amd/display: Use kernel alloc/free")
Assisted-by: Copilot:claude-opus-4.6
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Ray Wu <ray.wu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 3766856 )
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/amd/display/dc/basics/vector.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=31180638a33acad12c863132704a76536fb66211

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

The original Linux kernel CVE announcement for CVE-2026-53329 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53329

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: 5
  Paranoid ActionableScore: 7

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: IMPORTANT
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): IMPORTANT

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).