[CVE-2026-93110][MODERATE REGULAR] RDMA/core: Wait for RCU callbacks before unloading ib_core [ Upstream

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

CVE: CVE-2026-93110
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: RDMA/core: Wait for RCU callbacks before unloading ib_core [ Upstream
Commit: 82dfd1df456227279b1c8c648983a530f2612098
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=82dfd1df456227279b1c8c648983a530f2612098
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93110
Analysis date: Thu, 17 Sep 2026 13:00:36 -0400
ActionableScore: 1
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-2026-93110 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93110

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-2026-93110	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-93110 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:H/UI:N/S:U/C:L/I:L/A:H';*CWE-416;*CWE-672;CWE-362;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.2';DESCR 'An RCU lifetime bug in RDMA core can allow put_gid_ndev() to remain queued after ib_core unload has started. Because put_gid_ndev() is implemented in ib_core, a queued callback that runs after module text is unloaded can result in a use after free of module code and a kernel crash. For the CVSS the PR:H is used because reliable triggering normally requires local administrative control over module unload or equivalent kernel module management privileges. The issue is not network reachable and is tied to the module cleanup path rather than RDMA packet processing. Impact is at least denial of service via kernel crash. In the paranoid interpretation, limited confidentiality or integrity impact is kept possible because this is an RCU use after free of code lifetime, but practical privilege escalation is not strongly supported by the patch context.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)	YES	SIMPLEFIX NETWORK HARDWARE LINUS  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH	NO	NO	checked

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

ActionableScore=1
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=YES
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 1
* Paranoid score: 1
* No floor applied. Real UAF floors do not apply because host-admin-equivalent module unload is positively established.
* No cap applied.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

Positive signals:

* +2 Real UAF / lifetime violation. `put_gid_ndev()` is queued via `call_rcu()` and implemented in `ib_core`. If queued callbacks run after module unload, RCU may call code whose lifetime has ended.
* +1 Reliable kernel crash / strong DoS. Calling unloaded module text can realistically cause Oops, panic, or fatal kernel fault.

Negative signals:

* -2 Host-admin-equivalent privilege required. The vulnerable terminal path is `ib_core_cleanup()` during module unload, which normally requires host root or `CAP_SYS_MODULE`.

Material non-awarded signals:

* Controlled reclaim not demonstrated.
* Arbitrary write not demonstrated.
* Remote reachability not established.
* Local unprivileged trigger not established.
* Namespace-scoped privilege not established.
* Concrete repeated release/refcount mutation not established.
* Structured stale-object leverage not awarded because the demonstrated stale use is an RCU callback into unloaded module code, not attacker-shaped reused structured data.
* Weak LPE not awarded because no meaningful attacker-controlled reuse, callback replacement, credential manipulation, or boundary bypass is shown.
* Extra Availability not awarded because the same crash is already counted once.
* C/I not awarded merely because execution after module unload could theoretically interact with reused memory.

3. Reachability analysis

The complete trigger appears tied to unloading `ib_core` while an RCU callback already queued by `call_rcu()` still exists. Workqueue destruction stops producers but does not drain queued RCU callbacks, and `synchronize_rcu()` is not sufficient for queued callback completion. The operation is therefore local and module-management related.

Host-admin-equivalent privilege is positively established because unloading a kernel module normally requires host root or `CAP_SYS_MODULE`. No supplied evidence shows that an ordinary local user, a namespace-scoped capability, or a container-local privilege can unload `ib_core` or complete the full trigger chain. There is no direct RDMA packet or network-triggered path in the supplied patch. No special rare hardware penalty is applied, but the privilege requirement already dominates practical exposure.

Race/timing penalty is not applied separately. Although this is an asynchronous RCU lifetime ordering issue, the supplied evidence does not establish a narrow attacker-uncontrollable race beyond the queued-callback/module-unload ordering.

4. Primitive and severity interpretation

The exact primitive is an RCU/module lifetime violation: a callback function located in `ib_core` may remain queued after the module text is unloaded. This is a real UAF-style post-lifetime use of module code.

This is not a concrete repeated release/refcount case. There is no visible first `put()` that can destroy an object followed by a second lifetime mutation on the same dangling reference. It is also not a demonstrated controlled UAF reclaim or attacker-shaped replacement-object case.

PrimitiveClass is `CLASS_B` because a real kernel lifetime violation exists. The demonstrated consequence is kernel crash or DoS. The speculative consequence is broader corruption if unloaded module text memory were meaningfully reused, but the supplied patch does not establish attacker-controlled reuse, callback-pointer control, arbitrary read/write, or privilege escalation.

ImportantCandidate is `NO` because the complete trigger requires host-admin-equivalent module unload and no meaningful below-host-admin exploitation leverage is established. AutoDowngradeAllowed is `YES` because this is a constrained privileged cleanup/unload lifetime bug with crash as the demonstrated result and no unresolved security-boundary or repeated-refcount primitive.

5. One-sentence report phrase

An RCU callback implemented in `ib_core` may run after module unload if queued callbacks are not drained, causing execution of unloaded module code and a privileged local kernel crash.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: this is a real RCU lifetime/UAF-style issue, but the supplied evidence points to a host-admin module-unload DoS path without demonstrated unprivileged reachability or exploitation leverage beyond crash.

7. Call-site confidence

Call-site confidence: medium

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

Patch: RDMA/core: Wait for RCU callbacks before unloading ib_core [ Upstream
Commit: 82dfd1df456227279b1c8c648983a530f2612098
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=82dfd1df456227279b1c8c648983a530f2612098

Changed files:
  drivers/infiniband/core/device.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=82dfd1df456227279b1c8c648983a530f2612098

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

The original Linux kernel CVE announcement for CVE-2026-93110 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93110

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: 1

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).