[CVE-2026-46178][LOW] RDMA/mlx4: Fix resource leak on error in mlx4_ib_create_srq()

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

CVE: CVE-2026-46178
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: RDMA/mlx4: Fix resource leak on error in mlx4_ib_create_srq()
Commit: c5dc30da990045105c9762248d23076223e7878a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c5dc30da990045105c9762248d23076223e7878a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46178
Analysis date: Thu, 28 May 2026 05:52:06 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A local user with access to mlx4 RDMA verbs can trigger an SRQ creation error path that leaks hardware resources, potentially causing resource exhaustion DoS after repeated attempts.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-46178 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46178

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-46178	LOW	CHECK	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-772;CWE-404;*CWE-401;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'An error unwind bug in RDMA mlx4 SRQ creation leaks the hardware SRQ resource when mlx4_srq_alloc succeeds but ib_copy_to_udata fails and the function exits without mlx4_srq_free. A local user with access to the mlx4 RDMA verbs device can trigger the failing udata copy path during SRQ creation, and repeated attempts may exhaust RDMA or kernel resources. For the CVSS the PR:L is used for the paranoid score because reliable triggering requires local code execution and access to the RDMA device node, but not full administrator privileges in common RDMA deployments. The issue is not network reachable by packet traffic. Impact is denial of service through resource exhaustion, with no evidence of memory corruption, information disclosure, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)	YES	INIT SIMPLEFIX LEAK NETWORK  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	NO	NO	guess

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ACTIONABLESCORE ANALYSIS
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ActionableScore=2
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: **1**
* Paranoid score: **2**
* Final recommended bucket: **Ordinary Moderate / Low-like**

## 2. Signal breakdown

* **Local unprivileged trigger: +1**
  A local process with access to the mlx4 RDMA verbs device can attempt SRQ creation and trigger the failing `ib_copy_to_udata()` unwind path.

* **Availability impact realistic: +1**
  Repeated triggering can leak SRQ or related device resources and may eventually cause RDMA resource exhaustion. This is not an immediate reliable kernel crash from a single operation.

* **Rare AND difficult-to-reach subsystem/configuration: -1**
  The issue requires mlx4 RDMA hardware and user access to the corresponding RDMA device interface. This is not a broadly exposed default kernel path.

No memory corruption, UAF, OOB write, privilege escalation primitive, information leak, or network trigger is supported by the patch.

## 3. Reachability analysis

The bug is reachable from local RDMA users that can create SRQ objects on mlx4 hardware. It does not appear reachable through ordinary network packet traffic. Namespaces or containers may matter only if RDMA device access is delegated into the container, but the attacker still needs local code execution and access to the RDMA verbs interface. The affected hardware and driver path are relatively specialized.

## 4. Severity interpretation

This behaves like an ordinary resource leak / resource exhaustion issue, not like an Important-class kernel vulnerability. The realistic impact is local DoS against RDMA or related kernel/device resources after repeated failed SRQ creation attempts. The patch does not indicate memory lifetime corruption, attacker-controlled overwrite, sensitive data exposure, or a plausible privilege escalation path.

## 5. One-sentence report phrase

A local user with access to mlx4 RDMA verbs can trigger an SRQ creation error path that leaks hardware resources, potentially causing resource exhaustion DoS after repeated attempts.

## 6. Manual review recommendation

**NO MANUAL CHECK NEEDED**

This is a constrained resource leak in a hardware-specific RDMA error path with no evidence of memory corruption, privilege escalation, or remote reachability.

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

Patch: RDMA/mlx4: Fix resource leak on error in mlx4_ib_create_srq()
Commit: c5dc30da990045105c9762248d23076223e7878a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c5dc30da990045105c9762248d23076223e7878a

Commit description:

Sashiko points out that mlx4_srq_alloc() was not undone during error
unwind, add the missing call to mlx4_srq_free().

Cc: stable@vger.kernel.org
Fixes: 225c7b1 ("IB/mlx4: Add a driver Mellanox ConnectX InfiniBand adapters")
Link: https://sashiko.dev/#/patchset/0-v1-e911b76a94d1%2B65d95-rdma_udata_rep_jgg%40nvidia.com?part=8
Link: https://patch.msgid.link/r/11-v1-41f3135e5565+9d2-rdma_ai_fixes1_jgg@nvidia.com
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/infiniband/hw/mlx4/srq.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=c5dc30da990045105c9762248d23076223e7878a

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

The original Linux kernel CVE announcement for CVE-2026-46178 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46178

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: 1
  Paranoid ActionableScore: 2

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).