[CVE-2026-93202][LOW] i3c: master: Fix recursive locking during device registration [ Upstream

[CVE-2026-93202][LOW] i3c: master: Fix recursive locking during device registration [ Upstream

[AL-KERNEL]

CVE: CVE-2026-93202
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: i3c: master: Fix recursive locking during device registration [ Upstream
Commit: b25232f66e8cd653d0c6bfdbe534e62a2f9d6a1b
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b25232f66e8cd653d0c6bfdbe534e62a2f9d6a1b
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93202
Analysis date: Fri, 18 Sep 2026 00:09:11 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-93202 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93202

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: NO

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

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

CVE-2026-93202	LOW	https://www.kernelcve.org/list/?q=CVE-2026-93202 CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';CWE-667;*CWE-833;CWE-662;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.4';DESCR 'I3C device registration can recursively acquire the same bus rwsem because i3c_master_register_new_i3c_devs calls device_register while holding the normal use bus lock. device_register can immediately run probe callbacks and those callbacks may call I3C helpers that try to take the same lock again. This can deadlock when a writer is waiting and can block I3C device registration or driver bind and unbind paths. For the CVSS the PR:H is used because reliable triggering normally requires administrative control of driver binding or device registration on the affected host. The issue is not network reachable and does not provide a memory corruption primitive. Impact is denial of service through a local subsystem deadlock rather than information disclosure or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0)	YES	OOB LOCK DEADLOCK INIT ERRORPATH HARDWARE  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	YES	NO	checked

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

ActionableScore=0
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=YES
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: -1
* Conservative score: 0
* Raw paranoid score: -1
* Paranoid score: 0
* Applied conservative floor/cap: raw score clamped from -1 to 0
* Applied paranoid floor/cap: raw score clamped from -1 to 0
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

Positive signals:

* +1 Local subsystem denial of service: recursive acquisition of the same I3C bus rwsem can deadlock when a writer is waiting and can block I3C device registration or driver bind and unbind paths.

Negative signals:

* -2 Host-admin-equivalent privilege required: the supplied trigger example uses sysfs driver unbind and bind operations for a host platform device, which require host administrative control.

Important non-awarded signals:

* RealUAF not awarded: no post-free object use, stale lifetime reference, double release, or refcount misuse is established.
* Memory corruption not awarded: the patch fixes lock ordering and registration sequencing, not OOB access, UAF, type confusion, or arbitrary write.
* Controlled reclaim not demonstrated.
* Arbitrary write not demonstrated.
* Confidentiality and integrity not awarded: no disclosure path or unauthorized data modification is shown.
* Remote reachability not established: this is not triggered by network traffic.
* Structured stale-object leverage not awarded: no stale object is consumed after free.
* Weak LPE not awarded: recursive locking and deadlock do not create a privilege escalation primitive.
* Extra Availability not awarded: the only supported effect is the same local subsystem deadlock.
* Concrete repeated release/refcount not awarded: there is no first release that may end lifetime followed by a second lifetime mutation on the same dangling reference.
* Race penalty not applied: this is a lock-ordering bug, but no separate narrow timing race penalty is needed.

3. Reachability analysis

The demonstrated trigger involves rebinding an Intel LPSS I3C platform driver through sysfs. That operation is host administrative device-management activity. The vulnerable path is reached during I3C device discovery and registration when `i3c_master_register_new_i3c_devs()` calls `device_register()` while holding the normal-use bus lock.

Ordinary unprivileged reachability is not established. Namespace-scoped privilege is not applicable because this is a host I3C bus and platform-device registration path, not a namespace-local network or user namespace object. There is no evidence that an attacker can instantiate or rebind the relevant I3C master controller from an unprivileged namespace.

Prior host setup exists in the practical sense that affected I3C hardware and driver binding must exist on the host. The code path is hardware and driver specific, but no additional rare-hardware penalty is needed because the host-admin requirement already dominates practical reachability. The issue is not network reachable. The deadlock condition depends on recursive rwsem acquisition with a waiting writer, but the supplied lockdep trace and locking design make the bug credible without needing to model a hard exploit race.

4. Primitive and severity interpretation

The exact primitive is recursive rwsem locking during I3C device registration. `device_register()` can synchronously trigger probe callbacks while the I3C bus normal-use lock is already held. Those callbacks may invoke I3C helpers that try to acquire the same rwsem again. Linux rwsems do not support recursive read locking in the presence of a waiting writer, so the result can be a deadlock.

This is not active structured UAF and not fixed stale storage. It is a lock-ordering and synchronization bug. There is no concrete repeated release/refcount operation. No first lifetime operation frees or destroys an object, and no second lifetime mutation through a dangling reference is present.

PrimitiveClass is NONE because the patch establishes no meaningful corruption, lifetime, ownership, authorization, or security-boundary primitive. The demonstrated consequence is denial of service through a local I3C registration or bind/unbind deadlock. A broader host-wide hang is possible only as an availability effect of the blocked kernel path, not as a memory corruption or privilege-escalation primitive.

ImportantCandidate is NO because there is no unresolved kernel corruption or boundary-bypass primitive. AutoDowngradeAllowed is YES because the issue is host-admin-gated, crash/corruption-free, and limited to a local subsystem deadlock.

Likely operational severity: ordinary low to moderate availability issue, not an Important-class kernel security issue.

5. One-sentence report phrase

I3C device registration can deadlock because device_register may run probe callbacks while the I3C bus rwsem is already held, but reliable triggering requires host administrative driver or device management and no memory corruption or privilege escalation primitive is established.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: this is a host-admin-gated recursive locking deadlock with no UAF, no memory corruption, no authorization bypass, no network trigger, and no plausible unresolved Important-grade primitive.

7. Call-site confidence

Call-site confidence: high

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

Patch: i3c: master: Fix recursive locking during device registration [ Upstream
Commit: b25232f66e8cd653d0c6bfdbe534e62a2f9d6a1b
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b25232f66e8cd653d0c6bfdbe534e62a2f9d6a1b

Changed files:
  drivers/i3c/master.c
  include/linux/i3c/master.h

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=b25232f66e8cd653d0c6bfdbe534e62a2f9d6a1b

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

The original Linux kernel CVE announcement for CVE-2026-93202 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93202

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:L/PR:H/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.4

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: unknown
  Paranoid ActionableScore: 0

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).