[CVE-2026-74352][MODERATE 7.0] of: reserved_mem: avoid post-init UAF when alloc_reserved_mem_array() fails

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

CVE: CVE-2026-74352
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: of: reserved_mem: avoid post-init UAF when alloc_reserved_mem_array() fails
Commit: 6d28e6ad3c5c9248577f21057baa9bf16fa9ef3b
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6d28e6ad3c5c9248577f21057baa9bf16fa9ef3b
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74352
Analysis date: Sat, 15 Aug 2026 19:41:50 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A post-init use-after-free in OF reserved-memory handling can occur when early dynamic array allocation fails, leaving `reserved_mem` pointing to freed `__initdata` that may later be dereferenced by `of_reserved_mem_lookup()` and cause a crash or corrupted reserved-memory lookup.

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

The original Linux kernel CVE announcement for CVE-2026-74352 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74352

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-2026-74352	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:H/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-825;CWE-703;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.4';DESCR 'A post-init use-after-free can occur in the OF reserved memory code when alloc_reserved_mem_array() fails during boot. The global reserved_mem pointer may still reference the initial reserved_mem_array stored in __initdata, while reserved_mem_count remains nonzero. After init memory is freed, later calls to exported of_reserved_mem_lookup() can dereference freed memory and may crash the kernel or return corrupted reserved memory information. For the CVSS the PR:H value is used because reliable triggering normally requires control over boot time device tree or platform configuration, or conditions that make early memblock allocation fail. The issue is not network reachable and depends on local or platform level control rather than packet traffic. Impact is at least denial of service via kernel crash. In the paranoid score, confidentiality and integrity are raised because the bug class is use-after-free in kernel memory, so stale initdata reuse could theoretically affect lookup results or memory ownership decisions. YES REQUIRES MANUAL CHECK';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)  SKIP CVE-2026-74352 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: 00c9a452a235c61f099504783badd9a7675ff5a5 YES  NO NO unknown 	MAYBE	INIT NOMEMCHK UAF HARDWARE LINUS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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

ActionableScore=5
ActionableScoreLower=3

## 1. ActionableScore

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

## 2. Signal breakdown

Triggered signals:

* Generic memory corruption: +2
  The bug is a real post-init use-after-free. The global `reserved_mem` pointer may still reference `reserved_mem_array` stored in `__initdata`, which is freed after init.

* Real lifetime corruption: +1
  This is a stale pointer lifetime bug across the init to post-init boundary.

* Reliable kernel crash / strong DoS: +1
  `of_reserved_mem_lookup()` is exported for post-init use and can dereference freed memory if `reserved_mem_count` remains nonzero.

* Firmware-mediated external influence: +1
  The trigger depends on reserved-memory topology, device tree or platform configuration, and early boot allocation failure.

* Privileged kernel/device-management memory corruption path: +1
  The stale object describes reserved-memory metadata used by platform and device initialization paths.

Subtracting signals:

* Hard or unreliable special condition: -1
  Reliable triggering requires `alloc_reserved_mem_array()` failure during boot, which is not a normal runtime condition.

* Requires admin/root/platform control in typical deployments: -2
  Practical control usually requires boot-time device tree, firmware, platform configuration, or forced early memory allocation failure.

Paranoid-only impact signals:

* Confidentiality impact plausible: +1
  Stale initdata reuse could theoretically cause lookup of corrupted reserved-memory metadata.

* Integrity impact plausible: +1
  Incorrect reserved-memory lookup results could theoretically affect memory ownership or device-memory decisions, although no direct write primitive is shown.

Not awarded:

* Remote reachable: +0
  No network path.

* Local unprivileged trigger: +0
  Ordinary local users cannot normally force this boot-time allocation failure.

* Strong LPE plausibility: +0
  The patch shows UAF, but not attacker-controlled reclaim, object replacement, callback control, arbitrary write, or refcount takeover.

## 3. Reachability analysis

The bug is reachable only if dynamic allocation of the reserved-memory array fails during early boot. This usually requires unusual reserved-memory configuration, memory pressure during memblock allocation, overflow conditions, or platform controlled device tree input.

A normal unprivileged local user cannot reliably trigger the failure after the system has booted. Containers and namespaces do not materially lower the privilege requirement because the vulnerable state is created before userspace policy isolation is relevant.

The affected OF reserved-memory code is common on device-tree based systems, especially embedded and ARM platforms, but the failure condition is uncommon. Call-site confidence: medium, because the patch and commit identify the exported post-init lookup path, but not all downstream callers are shown.

## 4. Severity interpretation

This is not an ordinary Low correctness fix because it leaves a global exported lookup path pointing at freed `__initdata`. It is a real lifetime bug and therefore deserves manual review.

Realistically, exploitation looks constrained and likely manifests as a kernel crash or corrupted reserved-memory lookup under unusual boot-time conditions. The paranoid score is higher because stale kernel metadata after init can sometimes be more security relevant than a simple NULL dereference, but the patch does not show a controlled reclaim or direct privilege escalation primitive.

Overall this behaves like a borderline-to-actionable Moderate issue, not a strong Important candidate by default.

## 5. One-sentence report phrase

A post-init use-after-free in OF reserved-memory handling can occur when early dynamic array allocation fails, leaving `reserved_mem` pointing to freed `__initdata` that may later be dereferenced by `of_reserved_mem_lookup()` and cause a crash or corrupted reserved-memory lookup.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is a real kernel UAF across the init/post-init lifetime boundary, and although practical triggering requires privileged or platform-level boot control, stale reserved-memory metadata can affect sensitive device and memory ownership decisions.

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

Patch: of: reserved_mem: avoid post-init UAF when alloc_reserved_mem_array() fails
Commit: 6d28e6ad3c5c9248577f21057baa9bf16fa9ef3b
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6d28e6ad3c5c9248577f21057baa9bf16fa9ef3b

Commit description:

The global pointer 'reserved_mem' continues to reference the
reserved_mem_array which lives in __initdata if
alloc_reserved_mem_array() fails. of_reserved_mem_lookup() is
exported for post-init use, that would dereference freed memory
and trigger a use-after-free.

So reset reserved_mem_count to 0 when alloc_reserved_mem_array()
fails.

Fixes: 00c9a45 ("of: reserved_mem: Add code to dynamically allocate reserved_mem array")
Signed-off-by: Wandun Chen <chenwandun@lixiang.com>
Link: https://patch.msgid.link/20260604015332.3669384-1-chenwandun1@gmail.com
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/of/of_reserved_mem.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=6d28e6ad3c5c9248577f21057baa9bf16fa9ef3b

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

The original Linux kernel CVE announcement for CVE-2026-74352 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74352

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:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 6.4

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).