[CVE-2026-98431][LOW] RDMA/uverbs: Fix mmap_lock/disassociation_lock circular dependency [ Upstream

[CVE-2026-98431][LOW] RDMA/uverbs: Fix mmap_lock/disassociation_lock circular dependency [ Upstream

[AL-KERNEL]

CVE: CVE-2026-98431
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: RDMA/uverbs: Fix mmap_lock/disassociation_lock circular dependency [ Upstream
Commit: 426f54f20b79c5b164a0472ad3f6ba36afcd08c6
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=426f54f20b79c5b164a0472ad3f6ba36afcd08c6
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98431
Analysis date: Wed, 14 Oct 2026 23:15:07 -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-2026-98431 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98431

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-2026-98431	LOW	https://www.kernelcve.org/list/?q=CVE-2026-98431 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT LOW AEGIS_AS=0 LEGACY=LOW RESULT=SAME (legacy and Aegis reconciliation agree; DECISION: both LOW)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';*CWE-833;CWE-667;CWE-362;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'An ABBA lock order inversion between mmap_lock and disassociation_lock can deadlock RDMA uverbs VMA registration or fork against mmap disassociation during device teardown. A local process with access to an RDMA uverbs file can hold the mmap side while device removal or reload enters the reverse locking path. For the CVSS the PR:L value in the paranoid score reflects that an ordinary RDMA user can participate in the mmap or fork side, although reliable self triggering normally also depends on an administrative device disassociation event. The race requires a specific timing window, so AC:H is appropriate. The issue is not network reachable through RDMA traffic alone. The demonstrated primitive is lockup only, with no stale pointer, invalid memory access, UAF, or write primitive. Impact is denial of service and may block device teardown or affected tasks, but there is no grounded confidentiality or integrity impact. Automated impact decision path. The original SimpleNet classifier selected MODERATE. The primary LLM estimated paranoid CVSS 4.7 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE to LOW because the CVSS score, vector or bug class threshold rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS_AND_CIANNH. The independent weaker Aegis shadow evaluated CVSS 2.0 and ActionableScore 0 with primitive class CLASS_C and manual review NO. Its independently reconciled impact was LOW. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)	MAYBE	READ LOCK DEADLOCK INIT NETWORK HARDWARE LINUS  DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS_AND_CIANNH	-	-	checked

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

ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 1
* Paranoid score: 1
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +1 realistic deadlock and denial of service: the opposite acquisition order between `mmap_lock` and `disassociation_lock` forms a concrete ABBA cycle that can indefinitely block the involved operations.
* No privilege penalty: host-administrator control is shown for the `devlink reload` example, but the supplied evidence does not prove that every possible disassociation event requires an attacker with host-admin powers.
* No race penalty: concurrent mmap or fork and disassociation are required, but the evidence does not establish a sufficiently narrow or unreliable timing window for the explicit `-1` penalty.
* No additional availability point: blocking device teardown or related tasks is the same deadlock consequence already counted.
* No UAF, OOB access, refcount mutation, stale-object use, controlled overwrite, or authorization bypass is established.
* B5-R does not apply because there is no heap OOB write or retry-accumulated offset.
* B3-PENDING does not apply because there is no shared-backing write.
* B4-PENDING does not apply because no authorization decision changes from DENY to ALLOW.
* Remote reachability, controlled reclaim, arbitrary write, confidentiality impact, integrity impact, and privilege escalation are not established.

3. Reachability analysis

An RDMA uverbs user with an existing file and mapping can participate in the `mmap` or `fork` side of the deadlock. The opposite side is entered during uverbs mmap disassociation associated with RDMA device teardown, unregister, or reload. The supplied trace shows `devlink reload`, which normally represents an administrative control-plane operation, but it does not prove that host-admin control is required for every event capable of initiating disassociation.

The complete below-host-admin trigger is therefore unresolved. `HostAdminRequired` is `UNKNOWN`, rather than `YES` or `NO`. No evidence establishes that the complete operation is available through attacker-created namespaces, so `NamespaceScopedPrivilege` is also `UNKNOWN`.

An RDMA device, an open uverbs file, registered VMAs, and concurrent teardown are prerequisites. Network traffic alone does not reach the vulnerable lock ordering. The required overlap is concrete, but its practical repeatability by one below-host-admin attacker is not established.

4. Primitive and severity interpretation

The exact primitive is an ABBA circular locking dependency:

`mmap_lock -> disassociation_lock`

versus:

`disassociation_lock -> mmap_lock`

This is a concurrency and availability defect, not a memory-lifetime violation. No object is shown to be freed and subsequently used. There is no repeated release, stale refcount mutation, heap overwrite, semantic reinterpretation, or security-boundary bypass.

The demonstrated consequence is potential indefinite blocking of mmap, fork, device disassociation, or teardown paths. A broader host-wide failure is not established. The issue is therefore `CLASS_C`, with no useful corruption primitive remaining after excluding the deadlock.

`ImportantCandidate=NO` because no memory corruption, authorization bypass, cross-boundary effect, or exploitation leverage beyond DoS is supported. `AutoDowngradeAllowed=YES` because the defect is a constrained lock-ordering problem and no unresolved Important-preserving primitive exists.

5. One-sentence report phrase

An ABBA lock order inversion between RDMA uverbs mmap registration and device disassociation can deadlock concurrent mmap or fork and teardown operations, causing a local denial of service without evidence of memory corruption or privilege escalation.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

The patch and call paths clearly establish a lock-ordering DoS only, with no UAF, overwrite, authorization bypass, or unresolved corruption primitive.

7. Call-site confidence

Call-site confidence: high

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

Patch: RDMA/uverbs: Fix mmap_lock/disassociation_lock circular dependency [ Upstream
Commit: 426f54f20b79c5b164a0472ad3f6ba36afcd08c6
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=426f54f20b79c5b164a0472ad3f6ba36afcd08c6

Changed files:
  drivers/infiniband/core/rdma_core.c
  drivers/infiniband/core/uverbs_main.c
  include/rdma/uverbs_types.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=426f54f20b79c5b164a0472ad3f6ba36afcd08c6

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

The original Linux kernel CVE announcement for CVE-2026-98431 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98431

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:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: 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: 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).