[CVE-2026-89992][MODERATE REGULAR] cpuidle: dt_idle_genpd: kfree() the original name allocation

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

CVE: CVE-2026-89992
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: cpuidle: dt_idle_genpd: kfree() the original name allocation
Commit: 1312ae33b91430ec99e69cd3d47f0e50a4ebf54b
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1312ae33b91430ec99e69cd3d47f0e50a4ebf54b
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89992
Analysis date: Wed, 16 Sep 2026 09:04:47 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
An invalid free in `dt_idle_genpd` can occur because `pd->name` may point inside a `kasprintf()` allocation before cleanup passes it to `kfree()`, leading primarily to a local or boot-time kernel crash rather than a demonstrated privilege escalation.

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

The original Linux kernel CVE announcement for CVE-2026-89992 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89992

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: NO

A detailed explanation of the methodology and priority rules is included
at the end of this message.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-89992	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-89992 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:L/I:L/A:H';CWE-763;CWE-590;*CWE-664;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.2';DESCR 'dt_idle_pd_alloc() could store pd name as a basename pointer inside a kasprintf() allocation instead of keeping the original allocation address. Later cleanup can pass that interior pointer to kfree(), which is an invalid free and may corrupt allocator metadata or crash the kernel. For the CVSS the PR:H is used because reliable triggering usually requires administrative control over device tree based cpuidle power domain configuration or platform setup. The issue is not network reachable and is tied to local or boot time platform configuration paths. Impact is at least denial of service via kernel crash, with limited confidentiality or integrity impact kept only in the paranoid score because the primitive is an invalid free rather than a demonstrated arbitrary write.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)	YES	DANGER SIMPLEFIX HARDWARE LINUS  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH	YES	NO	checked

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

ActionableScore=2
PrimitiveClass=CLASS_B
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES

## 1. ActionableScore

* Raw conservative score: 2
* Conservative score: 2
* Raw paranoid score: 2
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate**::

No floor or cap was applied.

## 2. Signal breakdown

Positive signals:

* +1 Weak / indirect corruption candidate. `pd->name` may be changed from the original `kasprintf()` allocation pointer to an interior `kbasename()` pointer, and later passed to `kfree()`.
* +1 Reliable kernel crash / strong DoS. Freeing a non-base allocation pointer can trigger allocator checks, WARN, BUG, panic, or allocator state damage depending on configuration.

Negative or non-awarded signals:

* No `-2` host-admin penalty was applied because the supplied evidence strongly suggests platform or device-tree level control, but does not fully prove the complete trigger always requires host-admin-equivalent privilege.
* No remote reachability. This is not network-triggerable.
* No RealUAF. The bug is an invalid free of an interior pointer, not a post-free use of a stale object.
* No concrete repeated release/refcount signal. There is no established first release followed by a second lifetime mutation of the same dangling reference.
* No controlled reclaim or arbitrary write is demonstrated.
* No confidentiality or integrity point is awarded. Allocator corruption is possible in principle, but no disclosure, controlled overwrite, or privilege-impacting primitive is established.
* No extra Availability point. The same crash/invalid-free consequence is already counted once.

## 3. Reachability analysis

The affected path is in `drivers/cpuidle/dt_idle_genpd.c`, tied to device-tree based cpuidle power-domain setup and cleanup. The attacker model is not a normal local unprivileged user and not a network attacker. Practical triggering likely depends on platform configuration, device tree contents, boot-time initialization, error unwind, or privileged device-tree overlay style control.

Host-admin-equivalent privilege is plausible, but not conclusively proven from the supplied snippet alone, so `HostAdminRequired=UNKNOWN` rather than `YES`. No namespace-scoped capability path is indicated. No prior network exposure exists. No race is involved. No special external hardware attack surface is shown beyond the platform/device-tree environment.

## 4. Primitive and severity interpretation

The exact primitive is `kfree()` on a pointer that may no longer equal the start of the allocation returned by `kasprintf()`. This is an invalid free / ownership tracking bug. It is not a UAF and not a double free based on the supplied evidence.

This is best treated as constrained `CLASS_B` kernel lifetime/allocator misuse. The demonstrated consequence is kernel crash or allocator error. A stronger consequence such as controlled allocator corruption is theoretically possible in the broad bug class, but the patch does not establish attacker-controlled reclaim, attacker-selected target, useful overwrite, callback control, or privilege escalation.

`ImportantCandidate=NO` because the issue appears constrained to platform/device-tree setup paths and lacks meaningful unresolved exploitation leverage beyond crash. `AutoDowngradeAllowed=YES` because this is not a demonstrated security-boundary bypass, not a real UAF, not a repeated refcount mutation, and not a controlled corruption primitive.

## 5. One-sentence report phrase

An invalid free in `dt_idle_genpd` can occur because `pd->name` may point inside a `kasprintf()` allocation before cleanup passes it to `kfree()`, leading primarily to a local or boot-time kernel crash rather than a demonstrated privilege escalation.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: the primitive is a real invalid free in kernel allocator context, but available evidence supports mainly crash/DoS with constrained platform-level reachability.

## 7. Call-site confidence

Call-site confidence: medium

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

Patch: cpuidle: dt_idle_genpd: kfree() the original name allocation
Commit: 1312ae33b91430ec99e69cd3d47f0e50a4ebf54b
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1312ae33b91430ec99e69cd3d47f0e50a4ebf54b

Commit description:

dt_idle_pd_alloc() kasprintf()s the full node path, then points
pd->name at kbasename() of that string. dt_idle_pd_free() kfree()s
pd->name, which is no longer the start of the allocation.

Copy the basename instead.

Fixes: 9d976d6 ("cpuidle: Factor-out power domain related code from PSCI domain driver")
Signed-off-by: Linkai Gong <gonglinkai@kylinos.cn>
Cc: stable@vger.kernel.org
Signed-off-by: Ulf Hansson <ulfh@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/cpuidle/dt_idle_genpd.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=1312ae33b91430ec99e69cd3d47f0e50a4ebf54b

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

The original Linux kernel CVE announcement for CVE-2026-89992 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89992

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:L/I:L/A:H
  The Best / paranoid CVSS score: 5.2

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: unknown
  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: 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).