[CVE-2026-64303][IMPORTANT] spi: fsl-lpspi: terminate the RX channel on TX prepare failure path

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

CVE: CVE-2026-64303
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: spi: fsl-lpspi: terminate the RX channel on TX prepare failure path
Commit: ad370d1c7a9a832f77b2341513cd31188c9443af
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ad370d1c7a9a832f77b2341513cd31188c9443af
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64303
Analysis date: Sat, 25 Jul 2026 12:08:49 -0400
ActionableScore: 7
ActionableScore lower bound: 5
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A TX DMA prepare failure in fsl-lpspi can leave RX DMA running after SPI DMA buffers are unmapped, creating a DMA write after unmap condition with potential memory corruption or use after free.

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

The original Linux kernel CVE announcement for CVE-2026-64303 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64303

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.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-64303	IMPORTANT	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:H/I:H/A:H';*CWE-416;*CWE-787;*CWE-664;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'In the fsl-lpspi DMA transfer path, RX DMA may already be submitted and issued before the TX descriptor is prepared. If dmaengine_prep_slave_sg() fails for TX, the old error path can return while RX DMA continues writing to buffers that the SPI core may unmap after the failed transfer. This creates a DMA write after unmap condition with potential memory corruption or use after free rather than a simple warning. For the CVSS the PR:L is used for the paranoid score because a local user or service with access to an SPI device node or delegated SPI control may be able to initiate transfers without full administrative privileges. The issue is not network reachable. Impact is at least local denial of service via memory corruption and in the worst defensible case may allow confidentiality or integrity impact due to kernel memory corruption, so manual review is recommended.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7)	YES	DANGER ERRORPATH UAF DMAorINTERRUPT KPANIC MEMORY  KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7	YES	NO	checked

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

ActionableScore=7
ActionableScoreLower=5

## 1. ActionableScore

* Conservative score: 5
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged or low privileged trigger: +1. A local process or service with access to the SPI device path may initiate SPI transfers without full host root in some deployments.
* Generic memory corruption, strong corruption primitive: +2. The commit explicitly describes RX DMA continuing to write after DMA buffers may be unmapped, leading to potential memory corruption or use after free.
* Real lifetime corruption: +1. The bug is an async DMA lifetime mismatch where buffers can be unmapped while RX DMA is still active.
* Privileged kernel/device-management memory corruption path: +1. The corruption occurs in a DMA adjacent SPI controller driver path.
* Hard or unreliable condition: -1. Trigger requires TX DMA descriptor preparation failure after RX DMA has already been issued.
* Rare or hardware-specific exposure: -1. The affected path depends on the fsl-lpspi controller, DMA mode, and relevant SPI deployment.

Paranoid additional interpretation:

* Privilege escalation plausible: +1 to +2. DMA write after unmap can corrupt reused kernel memory and is stronger than a NULL dereference, but no controlled reclaim or reliable overwrite target is demonstrated.
* Availability impact realistic: +1. Kernel memory corruption or UAF can plausibly lead to a host crash.

## 3. Reachability analysis

This is not network reachable. The realistic trigger is local or device-mediated through an SPI transfer on systems using the fsl-lpspi driver in DMA mode. In typical embedded or SoC deployments, SPI access may be restricted to root or trusted services, but some systems expose SPI through device nodes or delegated services, making PR:L a defensible practical interpretation. Namespaces do not normally make SPI hardware access available by themselves, but container or service delegation can lower the practical privilege boundary.

Call-site confidence: high. The commit message states the relevant ordering directly: RX DMA is submitted and issued before TX descriptor preparation, and the SPI core may unmap DMA buffers after the function returns an error.

## 4. Severity interpretation

This is more than an ordinary Moderate correctness bug because the failed unwind path can leave DMA writing into memory after ownership has changed. The realistic impact is local DoS or kernel memory corruption under a hardware and error-path dependent condition. The theoretical worst case includes privilege escalation if the freed or unmapped buffer is reused in a controllable way, but the patch does not demonstrate a reliable reclaim or controlled overwrite primitive. Therefore the conservative bucket is Actionable Moderate, while the paranoid bucket is a Strong Important candidate for manual triage.

## 5. One-sentence report phrase

A TX DMA prepare failure in fsl-lpspi can leave RX DMA running after SPI DMA buffers are unmapped, creating a DMA write after unmap condition with potential memory corruption or use after free.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the patch explicitly fixes a DMA lifetime bug with potential memory corruption or UAF, and the practical severity depends on device exposure, DMA behavior, buffer reuse, and whether local SPI access is available to reduced privilege users or services.

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

Patch: spi: fsl-lpspi: terminate the RX channel on TX prepare failure path
Commit: ad370d1c7a9a832f77b2341513cd31188c9443af
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ad370d1c7a9a832f77b2341513cd31188c9443af

Commit description:

When dmaengine_prep_slave_sg() fails for the TX channel, the error path
terminates the TX DMA channel but leaves the RX channel running. Since
the RX channel was already submitted and issued prior to preparing
the TX descriptor, returning -EINVAL causes the SPI core to unmap the
DMA buffers while the RX DMA engine continues writing to them, leading
to potential memory corruption or use-after-free.

Terminate the RX channel before returning on the TX prepare failure path.

Fixes: 09c0446 ("spi: lpspi: add dma mode support")
Cc: stable@vger.kernel.org
Signed-off-by: Carlos Song <carlos.song@nxp.com>
Link: https://patch.msgid.link/20260525062357.3191349-3-carlos.song@oss.nxp.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/spi/spi-fsl-lpspi.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=ad370d1c7a9a832f77b2341513cd31188c9443af

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

The original Linux kernel CVE announcement for CVE-2026-64303 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64303

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:L/UI:N/S:U/C:L/I:L/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: 5
  Paranoid ActionableScore: 7

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).