[CVE-2026-72495][MODERATE REGULAR] RDMA/bnxt_re: Avoid repeated requests to allocate WC pages

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

CVE: CVE-2026-72495
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: RDMA/bnxt_re: Avoid repeated requests to allocate WC pages
Commit: 478c4d24193fe3e6aa2accd4874ae43000e4a217
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=478c4d24193fe3e6aa2accd4874ae43000e4a217
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72495
Analysis date: Sun, 16 Aug 2026 06:17:03 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Borderline manual review recommended / Ordinary Moderate
Manual review required: YES

Summary:
A local process with access to the bnxt_re RDMA uverbs interface could repeatedly or concurrently request WC page allocation for the same ucontext, causing inconsistent WC DPI resource accounting and possible RDMA resource exhaustion.

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

The original Linux kernel CVE announcement for CVE-2026-72495 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72495

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-2026-72495	MODERATE	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:L/UI:N/S:U/C:N/I:N/A:H';**CWE-400;*CWE-772;CWE-362;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'bnxt_re allowed repeated or concurrent WC page allocation requests for the same RDMA ucontext even though only one WC page is supported per context. A local process with access to the RDMA uverbs device could repeatedly request WC pages or race allocation and cleanup, causing inconsistent WC DPI resource accounting and possible exhaustion of limited doorbell resources. For the CVSS the PR:L is used because the attacker needs local access to the RDMA device interface, but does not necessarily need full administrator privileges in deployments where RDMA device nodes are delegated to users or containers. The issue is not network reachable directly and is triggered through local control plane operations on the RDMA userspace API. Impact is primarily denial of service against RDMA device resources rather than proven kernel memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline manual review recommended / Ordinary Moderate (with actual score 3)  SKIP CVE-2026-72495 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: eee6268421a2ccc6d47d8e175a1f4bfcd78a83ca YES  NO NO unknown 	MAYBE	READ LOCK INIT NETWORK MEMORY  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH	-	-	checked

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

ActionableScore=3
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 3
* Final recommended bucket: **Borderline manual review recommended / Ordinary Moderate**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. A local process with access to the RDMA uverbs device can request WC page allocation for its ucontext.
* Availability impact realistic: +1. Repeated WC allocation or failed mmap insertion can leak or exhaust limited WC DPI / doorbell resources and affect RDMA availability.
* Rare AND difficult-to-reach subsystem/configuration: -1. This is specific to Broadcom bnxt_re RDMA hardware and low latency push / WC doorbell support.
* No generic memory corruption: +0. The patch shows resource accounting, locking, and cleanup fixes, not UAF, OOB write, type confusion, arbitrary write, or callback corruption.
* No privilege escalation signal: +0. No supported LPE primitive is visible.
* No network reachability: +0. The vulnerable operation is local RDMA uverbs control-plane access, not packet-triggered network input.

Paranoid additional signal:

* Reliable device-resource DoS concern: +1. If WC DPI / doorbell resources are scarce, repeated requests or concurrent allocation attempts may cause practical RDMA device resource exhaustion for other users.

Call-site confidence: high. The relevant allocation, mmap insertion failure path, and cleanup path are visible in the provided patch.

## 3. Reachability analysis

The bug is reachable by a local process that can open and use the bnxt_re RDMA uverbs interface. This does not necessarily require full host root in deployments where RDMA device nodes are delegated to users, containers, or HPC workloads. It is not directly network-triggerable. Namespaces and containers matter because RDMA devices may be passed through or exposed to non-root workloads, making PR:L a reasonable practical interpretation. The affected path is not broadly default-exposed on generic Linux systems because it requires specific Broadcom RDMA hardware, driver support, and the WC / low-latency doorbell feature.

## 4. Severity interpretation

This behaves like an ordinary-to-borderline Moderate issue, not an Important-class vulnerability. The patch fixes repeated allocation, concurrent access, and missing cleanup for WC DPI resources. The realistic impact is local denial of service against RDMA device resources. There is no demonstrated kernel memory corruption primitive, no confidentiality impact, no integrity impact, and no plausible privilege escalation path from the supplied patch context. The paranoid score is higher only because resource exhaustion may be practical if limited hardware doorbell resources can be repeatedly consumed.

## 5. One-sentence report phrase

A local process with access to the bnxt_re RDMA uverbs interface could repeatedly or concurrently request WC page allocation for the same ucontext, causing inconsistent WC DPI resource accounting and possible RDMA resource exhaustion.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Manual review is recommended because this is a local RDMA userspace API resource accounting and concurrency bug, and deployments may delegate RDMA device access to non-root users or containers. It does not appear to require urgent Important-class handling unless product-specific RDMA exposure makes resource exhaustion easy and impactful.

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

Patch: RDMA/bnxt_re: Avoid repeated requests to allocate WC pages
Commit: 478c4d24193fe3e6aa2accd4874ae43000e4a217
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=478c4d24193fe3e6aa2accd4874ae43000e4a217

Commit description:

Applications can request multiple WC pages for the same ucontext.
As of now, only 1 WC page per ucontext is supported. Add a lock to
avoid concurrent access and a check to fail repeated requests.
Also, if the mmap entry insert fails for the WC, free the Doorbell
page index mapped for the WC page.

Fixes: eee6268 ("RDMA/bnxt_re: Move the UAPI methods to a dedicated file")
Fixes: 360da60 ("RDMA/bnxt_re: Enable low latency push")
Link: https://patch.msgid.link/r/20260615224751.232802-12-selvin.xavier@broadcom.com
Reviewed-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Signed-off-by: Selvin Xavier <selvin.xavier@broadcom.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/infiniband/hw/bnxt_re/ib_verbs.c
  drivers/infiniband/hw/bnxt_re/ib_verbs.h
  drivers/infiniband/hw/bnxt_re/uapi.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=478c4d24193fe3e6aa2accd4874ae43000e4a217

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

The original Linux kernel CVE announcement for CVE-2026-72495 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72495

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:L/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.5

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).