[CVE-2026-46189][IMPORTANT] RDMA/vmw_pvrdma: Fix double free on pvrdma_alloc_ucontext() error path

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

CVE: CVE-2026-46189
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: RDMA/vmw_pvrdma: Fix double free on pvrdma_alloc_ucontext() error path
Commit: ecc36a82ecfcfdf3c6606d209f22ec5543c410e0
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ecc36a82ecfcfdf3c6606d209f22ec5543c410e0
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46189
Analysis date: Thu, 28 May 2026 10:11:28 -0400
ActionableScore: 8
ActionableScore lower bound: 6
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
`pvrdma_alloc_ucontext()` can double free the same UAR on an `ib_copy_to_udata()` failure path, allowing a local user with PVRDMA uverbs access to trigger kernel memory corruption and likely DoS, with possible LPE concern.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-46189 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46189

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-2026-46189	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/vmw_pvrdma pvrdma_alloc_ucontext could free the same UAR twice when ib_copy_to_udata() failed on the ucontext creation error path. A local user with access to the VMware PVRDMA uverbs device can trigger the failing copy path by providing an invalid userspace response buffer, without full host administrative privileges once the RDMA device is exposed. For the CVSS the PR:L is used because access to the uverbs device or an equivalent delegated RDMA context is sufficient in the paranoid scenario. The issue is not network reachable by itself. Impact is at least local denial of service through kernel crash or resource corruption, and worst case may allow confidentiality or 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)  SKIP CVE-2026-46189  SKIP The Fixes patch not applied yet, so unlikely that actual: 29c8d9eba550 YES  NO NO unknown 	MAYBE	DANGER INIT SIMPLEFIX ERRORPATH NETWORK 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 the VMware PVRDMA uverbs device can reach `pvrdma_alloc_ucontext()`.
* Generic memory corruption: +2. The bug is a real double free of the UAR object on the error path.
* Real lifetime corruption: +1. The same resource is freed explicitly and then again via `pvrdma_dealloc_ucontext()`.
* Reliable kernel crash / strong DoS: +1. Double free can corrupt allocator or driver state and plausibly crash the kernel.
* Local high-control device API: +1. RDMA uverbs exposes structured user-driven object creation and error paths.
* Constrained primitive: -1. The patch does not show a controlled reclaim or overwrite target.

Paranoid additional signals:

* Weak to strong LPE concern: +1. Double free is a kernel memory corruption primitive, but exploitability depends on UAR allocation behavior and object reuse control.
* Privileged device-management memory corruption path: +1. The corruption is in an RDMA device context allocation path.

## 3. Reachability analysis

The issue is locally reachable by users with access to a VMware PVRDMA uverbs device. The trigger is the ucontext creation error path when copying response data to userspace fails.

No network reachability is shown by the patch. Containers matter if the PVRDMA or uverbs device is passed through to a container, in which case a reduced-privilege workload may trigger the bug without host root. If the device is unavailable or restricted to trusted users, practical exposure is lower.

## 4. Severity interpretation

This behaves like an Important candidate under paranoid triage and at least an actionable Moderate. The realistic impact is local DoS through kernel crash or resource corruption.

The higher concern is possible privilege escalation because the primitive is a real kernel double free, but no concrete arbitrary write or exploit chain is demonstrated by the patch.

## 5. One-sentence report phrase

`pvrdma_alloc_ucontext()` can double free the same UAR on an `ib_copy_to_udata()` failure path, allowing a local user with PVRDMA uverbs access to trigger kernel memory corruption and likely DoS, with possible LPE concern.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

This is a real kernel double free in an RDMA uverbs error path, and impact depends on device exposure, container delegation, and allocator reuse controllability.

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UPSTREAM PATCH SUMMARY
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Patch: RDMA/vmw_pvrdma: Fix double free on pvrdma_alloc_ucontext() error path
Commit: ecc36a82ecfcfdf3c6606d209f22ec5543c410e0
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ecc36a82ecfcfdf3c6606d209f22ec5543c410e0

Commit description:

Sashiko points out that pvrdma_uar_free() is already called within
pvrdma_dealloc_ucontext(), so calling it before triggers a double free.

Cc: stable@vger.kernel.org
Fixes: 29c8d9e ("IB: Add vmw_pvrdma driver")
Link: https://sashiko.dev/#/patchset/0-v1-e911b76a94d1%2B65d95-rdma_udata_rep_jgg%40nvidia.com?part=4
Link: https://patch.msgid.link/r/10-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/vmw_pvrdma/pvrdma_verbs.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=ecc36a82ecfcfdf3c6606d209f22ec5543c410e0

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

The original Linux kernel CVE announcement for CVE-2026-46189 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46189

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).