[CVE-2026-98252][MODERATE REGULAR] RDMA/core: fix refcount bug in iwpm_get_nlmsg_request()

[CVE-2026-98252][MODERATE REGULAR] RDMA/core: fix refcount bug in iwpm_get_nlmsg_request()

[AL-KERNEL]

CVE: CVE-2026-98252
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: RDMA/core: fix refcount bug in iwpm_get_nlmsg_request()
Commit: 52c13c63bb3662c108244e7447055e30bf40244e
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=52c13c63bb3662c108244e7447055e30bf40244e
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98252
Analysis date: Sat, 10 Oct 2026 13:35:38 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Borderline / manual review recommended
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-98252 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98252

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: YES

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

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

CVE-2026-98252	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98252 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=0 LEGACY=MODERATE RESULT=DIFF (independent Legacy and Aegis differ; FINAL: MODERATE, Aegis: MODERATE_KPANIC)	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-362;CWE-665;CWE-911;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A race in `iwpm_get_nlmsg_request()` exposes a newly allocated IWPM request through the global list before its reference count and remaining fields are initialized. Another CPU can find the request and call `kref_get()` while the reference count is still zero, causing an addition on zero warning and creating an inconsistent object lifetime state. Concurrent code may also observe partially initialized request fields. The demonstrated impact is a local kernel warning or denial of service, while the reference count inconsistency provides a plausible use after free candidate that may have confidentiality or integrity impact in the worst defensible case. For the CVSS the PR:L is selected because an attacker needs local user or process access to exercise the RDMA or iWARP control path, but full administrative control is not necessarily required when RDMA access is available to unprivileged applications. AC:H is selected because successful triggering depends on another CPU accessing the global list during the narrow interval before initialization completes. The issue is not directly reachable through ordinary remote network traffic and normally requires an active iWARP configuration and its port mapper path. Impact is at least a local denial of service and in the worst case may include privilege escalation through object lifetime corruption, which requires manual validation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3)	MAYBE	LOCK DANGER SIMPLEFIX NETWORK HARDWARE LINUS SYZBOT  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4	-	-	checked

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

ActionableScore=3
ActionableScoreLower=2
PrimitiveClass=CLASS_B
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw conservative score: 2
* Conservative score: 2
* Raw paranoid score: 3
* Paranoid score: 3
* No floor or cap was applied.
* Final recommended bucket: **Borderline / manual review recommended**::

2. Signal breakdown

Conservative signals:

* +2 Concrete Class B refcount and lifetime-state corruption. The object is published in a global list while its kref is zero, allowing another CPU to execute a real `kref_get()` against invalid lifetime state. A later `kref_init()` can overwrite concurrently modified accounting.
* No race penalty. The interleaving is required, but the evidence does not establish that repeated attempts are prohibitively difficult or externally uncontrollable.
* Total: 2.

Paranoid additional signal:

* +1 Weak structured invalid-state consumption. The patch deliberately moves initialization of every field before publication, and the demonstrated global visibility means another CPU can potentially observe fields such as sequence, callback, semaphore, and error state before initialization. This is technically defensible but not proven to produce a useful exploitation primitive.
* Total: 3.

Important non-awarded signals:

* Real UAF was not established. Here the zero kref belongs to a newly allocated but not yet initialized object, rather than an object proven to have been freed.
* No concrete second release or refcount decrement through a dangling reference is shown.
* Concrete repeated release/refcount +1 was not awarded.
* Paranoid repeated-refcount leverage +1 was not awarded.
* FLOOR 5 was not applied.
* Reliable kernel crash +1 was not awarded because the supplied evidence demonstrates an addition-on-zero warning, not a normal-configuration panic.
* Controlled reclaim, refcount takeover, arbitrary write, disclosure, callback control, and privilege escalation are not demonstrated.
* Remote reachability and ordinary unprivileged reachability are not established.
* B5-R does not apply because no heap OOB write or retry-accumulated offset exists.
* B3-PENDING does not apply because no shared-backing write exists.
* B4-PENDING does not apply because no authorization decision is bypassed.

3. Reachability analysis

The vulnerable operation belongs to the iWARP Port Mapper request path. Triggering requires creation of an IWPM request and concurrent lookup of the globally published request during its initialization window.

The supplied patch does not establish whether an ordinary local user, an RDMA service account, or only an administrator can drive the complete sequence. The previous PR:L assessment is plausible where unprivileged RDMA applications can reach the relevant path, but this is not sufficiently established here to set `HostAdminRequired=NO` or award a local-unprivileged bonus.

No evidence resolves whether namespace-scoped capabilities are sufficient. An active iWARP and IWPM configuration is a prerequisite, but the evidence does not show that unusual physical hardware or host-admin-only setup is mandatory. Ordinary remote network traffic does not directly invoke the vulnerable list publication race.

4. Primitive and severity interpretation

The exact primitive is premature publication of an active structured request object followed by concurrent mutation of an uninitialized kref. This is a concrete refcount and initialization-order corruption issue, so `CLASS_B` is appropriate.

It is not a confirmed UAF because no execution path proves that the request is freed and subsequently used. It is also not a concrete repeated-release case because the patch does not show an initial lifetime-ending put followed by another mutation through the same dangling reference.

The demonstrated consequence is a refcount addition-on-zero warning. A kernel fault or later lifetime failure is plausible if reference accounting becomes inconsistent or another field is consumed prematurely, but controlled post-free use and non-crash exploitation are not established.

`ImportantCandidate=NO` because no real UAF, controlled lifetime takeover, repeated stale refcount mutation, or other Important-preserving primitive is proven. `AutoDowngradeAllowed=YES` because the remaining issue is a constrained Class B initialization/refcount race without demonstrated meaningful exploitation leverage. Manual review remains recommended to inspect list lookup, removal, and kref put call sites.

5. One-sentence report phrase

A race publishes an IWPM request before its reference count and fields are initialized, allowing another CPU to increment a zero kref and potentially consume inconsistent request state.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Review all `iwpm_nlmsg_req_list` lookup, removal, and `kref_put()` paths to determine whether the lost or overwritten reference can cause a concrete premature free and post-free use.

7. Call-site confidence

Call-site confidence: medium

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

Patch: RDMA/core: fix refcount bug in iwpm_get_nlmsg_request()
Commit: 52c13c63bb3662c108244e7447055e30bf40244e
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=52c13c63bb3662c108244e7447055e30bf40244e

Commit description:

iwpm_get_nlmsg_request() initializes refcount _after_ list_add_tail()
making it accessible to global list where another CPU can kref_get()
on nlmsg_request causing a refcount "addition on 0" bug. Fix this
by initializing kref _before_ list_add_tail() so refcount for
nlmsg_request can be incremented/decremented normally. In addition,
also initialize every field before list_add_tail().

Reported-by: syzbot+bd317784d628820741b5@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=bd317784d628820741b5
Fixes: 30dc5e6 ("RDMA/core: Add support for iWARP Port Mapper user space service")
Cc: stable@vger.kernel.org
Signed-off-by: Jeffin Philip <jeffinphilip14@gmail.com>
Link: https://patch.msgid.link/20260904131437.12917-1-jeffinphilip14@gmail.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/infiniband/core/iwpm_util.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=52c13c63bb3662c108244e7447055e30bf40244e

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

The original Linux kernel CVE announcement for CVE-2026-98252 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98252

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:N/I:N/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: 2
  Paranoid ActionableScore: 3

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).