[CVE-2026-45852][IMPORTANT] RDMA/rxe: Fix double free in rxe_srq_from_init [ Upstream

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

CVE: CVE-2026-45852
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: RDMA/rxe: Fix double free in rxe_srq_from_init [ Upstream
Commit: 22b8c23a3b92d023614bb00896fe364b2c1a31d3
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=22b8c23a3b92d023614bb00896fe364b2c1a31d3
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45852
Analysis date: Thu, 28 May 2026 00:48:17 -0400
ActionableScore: 8
ActionableScore lower bound: 6
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
RDMA RXE SRQ creation can leave a freed queue pointer in `srq->rq.queue` after `copy_to_user()` failure, causing a later cleanup path to double free the same kernel object and potentially crash the system or enable memory-corruption impact.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-45852 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45852

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: IMPORTANT
Manual review required: YES

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-2026-45852	IMPORTANT	CHECK	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-415;*CWE-416;*CWE-664;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'RDMA/rxe rxe_srq_from_init stored the allocated queue pointer in srq rq queue before copy_to_user completed. If copy_to_user failed, the error path freed the queue but left the stale pointer in the SRQ object, and the later rxe_srq_cleanup path could free the same queue again. For the CVSS the PR:L is used because a local user with access to an RDMA uverbs or RXE device can attempt SRQ creation with a failing user response pointer, without full host administrative privileges once the device is available. The issue is not network reachable by itself. Impact is at least local denial of service through allocator corruption or kernel crash, and worst case may allow confidentiality and integrity impact because double-free is a kernel memory corruption primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 8) 	MAYBE	INIT LEAK NETWORK LINUS KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=8
ActionableScoreLower=6

## 1. ActionableScore

* Conservative score: 6
* Paranoid score: 8
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. A local user with access to RDMA uverbs/RXE can trigger SRQ creation and force `copy_to_user()` failure with an invalid userspace response pointer.
* Generic memory corruption: +2. The bug is a real kernel double free of the RXE queue object.
* Real lifetime corruption: +1. A freed queue pointer remains stored in `srq->rq.queue` and is later reused by cleanup.
* Reliable kernel crash / strong DoS: +1. Double free in allocator paths can reliably corrupt allocator state or crash the kernel.
* Local high-control kernel device API: +1. RDMA uverbs exposes structured user-controlled operations for object creation and lifetime.
* Privileged kernel/device-management memory corruption path: +1. The corruption occurs in RDMA device object management.
* Constrained primitive / no demonstrated payload control: -1. The patch shows double free, but not a demonstrated controlled reclaim or overwrite target.

Paranoid additional interpretation:

* Weak to moderate LPE concern: +1. Double free is a strong memory-corruption class, and local users may be able to shape RDMA object allocation patterns, but no concrete exploit primitive is shown.
* Availability impact realistic: +1. The expected practical impact is system-wide kernel crash or allocator corruption.

## 3. Reachability analysis

The bug is locally reachable through RDMA RXE/uverbs SRQ creation. It does not require network reachability by itself. The attacker needs access to an RDMA uverbs or RXE device node, which is often restricted but may be delegated to non-root users in RDMA, HPC, or container environments.

Namespaces and containers matter if `/dev/infiniband/uverbsX` or an RXE device is passed into a container. In that case, a containerized workload may trigger the bug without full host root. Creating or configuring RXE devices may require administrative privileges, but triggering the vulnerable SRQ creation path can be lower privilege once the device is available.

RXE is not a universal default path on all systems, but it is reachable through ordinary local RDMA interfaces where enabled.

## 4. Severity interpretation

This behaves more like an Important candidate than an ordinary Moderate issue. The realistic impact is local DoS through kernel crash or allocator corruption. The theoretical impact includes possible privilege escalation because the primitive is a real double free in kernel heap object lifetime handling.

There is no evidence of remote exploitation, arbitrary write, or a demonstrated LPE chain in the patch. The higher paranoid score is justified by the double-free class and local uverbs reachability, not by proven code execution.

## 5. One-sentence report phrase

RDMA RXE SRQ creation can leave a freed queue pointer in `srq->rq.queue` after `copy_to_user()` failure, causing a later cleanup path to double free the same kernel object and potentially crash the system or enable memory-corruption impact.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

This is a kernel double free reachable from a local RDMA uverbs/RXE operation, and the practical risk depends on device-node exposure, container delegation, and allocator reclaim controllability.

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

Patch: RDMA/rxe: Fix double free in rxe_srq_from_init [ Upstream
Commit: 22b8c23a3b92d023614bb00896fe364b2c1a31d3
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=22b8c23a3b92d023614bb00896fe364b2c1a31d3

Changed files:
  drivers/infiniband/sw/rxe/rxe_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=22b8c23a3b92d023614bb00896fe364b2c1a31d3

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

The original Linux kernel CVE announcement for CVE-2026-45852 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45852

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: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: 6
  Paranoid ActionableScore: 8

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: IMPORTANT
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): IMPORTANT

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).