[CVE-2026-64020][LOW] nvme-pci: fix dma_vecs leak on p2p memory [ Upstream

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

CVE: CVE-2026-64020
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: nvme-pci: fix dma_vecs leak on p2p memory [ Upstream
Commit: 24ea0de233d9ebb5ebd6f6018eaf2084af25e3dd
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=24ea0de233d9ebb5ebd6f6018eaf2084af25e3dd
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64020
Analysis date: Sun, 19 Jul 2026 12:05:52 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A dma_vecs allocation leak in the nvme-pci P2P PRP mapping path can cause local resource exhaustion under specialized NVMe P2P configurations, but it does not show evidence of memory corruption or privilege escalation.

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

The original Linux kernel CVE announcement for CVE-2026-64020 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64020

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-2026-64020	LOW	CHECK WITH IMPACT FROM ORIG NN 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-401;*CWE-772;**CWE-400;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'A dma_vecs memory leak in the nvme-pci PRP mapping path can occur for P2P memory because the driver tracks DMA mapping state even though P2P memory is not unmapped in this path. Repeated I/O using P2P memory can accumulate leaked allocations and may eventually cause local resource exhaustion or system instability. For the CVSS the PR:L in the paranoid score represents environments where a local low privileged user can repeatedly submit I/O through an exposed NVMe device and the required P2P setup already exists. The issue is not network reachable and there is no evidence of UAF, OOB access, arbitrary write, information disclosure, or privilege escalation. Impact is denial of service only via memory exhaustion under specialized hardware and configuration conditions.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)  SKIP CVE-2026-64020 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: b8b7570a7ec872f2a27b775c4f8710ca8a357adf YES  NO NO unknown 	MAYBE	SIMPLEFIX NVME LEAK DMAorINTERRUPT LINUS MEMORY  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	-	-	checked

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

ActionableScore=2
ActionableScoreLower=1

## 1. ActionableScore

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

## 2. Signal breakdown

Conservative signals:

* Important filesystem/storage path: +1. The bug is in the NVMe PCI host driver PRP mapping path.
* Availability impact realistic: +1. Repeated leaked dma_vec allocations could cause resource exhaustion.
* Requires specialized P2P memory setup: -1. The issue depends on NVMe P2P memory usage, which is not a common default path.
* Requires privileged or preconfigured environment in typical deployments: -1. Practical triggering normally depends on an administrator configured NVMe P2P capable setup.

Paranoid signals:

* Local low privileged trigger: +1. If the P2P setup already exists and a local user can repeatedly submit I/O through the exposed NVMe device.
* Availability impact realistic: +1. Sustained repeated I/O could accumulate leaked allocations.
* Important filesystem/storage path: +1. NVMe host I/O is a storage path.
* Rare and difficult to reach configuration: -1. P2P memory for NVMe is specialized.

No memory corruption, UAF, double free, OOB write, arbitrary write, page-cache corruption, confidentiality impact, integrity impact, or privilege escalation primitive is supported by the patch.

## 3. Reachability analysis

The bug is local and configuration dependent. It requires NVMe PCI operation with P2P memory, and the leak occurs because P2P memory is tracked for DMA unmap even though it is not unmapped in this path. In typical deployments, setting up P2P capable NVMe paths is an administrative or specialized storage configuration task. A low privileged user might only trigger repeated I/O if the device and P2P path are already exposed to that user. Containers and namespaces do not generally make this broadly reachable unless the NVMe device is explicitly delegated.

## 4. Severity interpretation

This behaves like a resource leak DoS issue, not an Important class kernel vulnerability. The realistic impact is memory/resource exhaustion after repeated operations under specialized hardware and configuration conditions. The theoretical worst case remains availability only. There is no evidence of memory corruption or privilege escalation.

## 5. One-sentence report phrase

A dma_vecs allocation leak in the nvme-pci P2P PRP mapping path can cause local resource exhaustion under specialized NVMe P2P configurations, but it does not show evidence of memory corruption or privilege escalation.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This can be auto-closed or deprioritized in most triage workflows because it is a specialized local resource leak with no supported memory corruption, confidentiality, integrity, or privilege escalation primitive.

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

Patch: nvme-pci: fix dma_vecs leak on p2p memory [ Upstream
Commit: 24ea0de233d9ebb5ebd6f6018eaf2084af25e3dd
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=24ea0de233d9ebb5ebd6f6018eaf2084af25e3dd

Changed files:
  drivers/nvme/host/pci.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=24ea0de233d9ebb5ebd6f6018eaf2084af25e3dd

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

The original Linux kernel CVE announcement for CVE-2026-64020 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64020

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: 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).