[CVE-2026-90012][MODERATE 7.0] spi: Fix DMA mapping ownership on partial map failure

[CVE-2026-90012][MODERATE 7.0] spi: Fix DMA mapping ownership on partial map failure

[AL-KERNEL]

CVE: CVE-2026-90012
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: spi: Fix DMA mapping ownership on partial map failure
Commit: cc8354213ad6bd5fb8cc05a3fa3701188d086626
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cc8354213ad6bd5fb8cc05a3fa3701188d086626
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90012
Analysis date: Wed, 16 Sep 2026 13:16:39 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-90012 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90012

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: MODERATE 7.0
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-2026-90012	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-90012 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:L/I:L/A:H';CWE-755;CWE-763;**CWE-476;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'A DMA mapping ownership bug in the SPI core can occur when __spi_map_msg sees a partial mapping failure. If RX mapping fails after TX mapping succeeds, tx_sg_mapped can remain set even though TX was already unmapped. If TX mapping fails on a later transfer, mappings from earlier transfers can remain active and later spi_unmap_msg may use a NULL or stale DMA device or release the same mapping twice. This can trigger a kernel oops through a NULL device dereference and may create limited DMA resource ownership risk. For the CVSS the PR:L is used because reliable triggering normally requires local ability to submit SPI transfers or control a local service or device node that can reach the SPI controller. The issue is not network reachable. Impact is at least local denial of service via kernel crash, with conservative limited confidentiality or integrity impact in the paranoid score due to stale device and double unmap behavior.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate (with actual score 5)  SKIP CVE-2026-90012 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	NULLPTR DMAorINTERRUPT HARDWARE KPANIC MEMORY 	-	-	checked

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

ActionableScore=5
ActionableScoreLower=4
PrimitiveClass=CLASS_B
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=REQUIRED
AutoDowngradeAllowed=NO

1. ActionableScore

* Raw conservative score: 4
* Conservative score: 4. No floor or cap changed it.
* Raw paranoid score: 5
* Paranoid score: 5. No floor or cap changed it.
* Final recommended bucket: **Actionable Moderate**::

2. Signal breakdown

Conservative signals:

* +1 Constrained kernel DMA ownership primitive. The patch establishes inconsistent DMA mapping ownership state where mappings may be released using a NULL or stale device, or the same mapping may be unmapped again.
* +1 Active state retirement and unwind bypass. The old error paths returned directly or manually unmapped only part of the state instead of unwinding all active mappings through the normal message unmap path.
* +1 Concrete resource or mapping management defect. Earlier DMA mappings can remain active after a later transfer mapping failure, with mapping flags and owner devices out of sync.
* +1 Reliable kernel crash or strong DoS. The commit explicitly states that using a NULL device in dma_unmap_sg_attrs can trigger an oops.

Paranoid additional signal:

* +1 Unresolved DMA ownership corruption leverage. The stale device and double unmap behavior affects DMA/IOMMU ownership state, which is stronger than a pure NULL dereference even though no controlled corruption primitive is demonstrated.

Non-awarded signals:

* RealUAF not awarded. The evidence shows stale DMA owner state and possible stale device use, but not a directly established heap object use-after-free.
* Concrete repeated release/refcount signal not awarded. dma_unmap is a mapping release operation, but the supplied control flow does not establish a classic object lifetime refcount put/free on the exact same dangling object.
* First release can end lifetime: not established for a kernel object lifetime reference.
* Exact same object reference survives for second lifetime mutation: not established in the repeated-refcount sense.
* Second operation mutates lifetime/refcount: not established. It mutates DMA mapping/IOMMU ownership state instead.
* FLOOR 5 was not applied as a UAF floor because RealUAF=NO. The paranoid score reaches 5 through DMA ownership risk, not a UAF floor.
* Controlled reclaim not demonstrated.
* Arbitrary write not demonstrated.
* Confidentiality and integrity impact not directly awarded. The limited C/I concern belongs only to paranoid interpretation of DMA ownership risk, not a demonstrated read/write primitive.
* Remote reachability not established.
* Race penalty not applied. This is an ordered partial failure and unwind bug, not a proven hard timing race.
* Extra availability not awarded. The oops is already counted once.

3. Reachability analysis

The vulnerable path is in the SPI core during DMA mapping of a spi_message. Triggering requires the ability to submit SPI transfers that use DMA and to hit a partial mapping failure sequence, for example RX mapping failure after TX mapping success or TX mapping failure after earlier transfers were mapped.

Below-host-admin reachability is plausible on systems exposing SPI through spidev, device-specific user interfaces, or local services, but the supplied evidence does not prove the complete trigger chain for an ordinary unprivileged user. Therefore HostAdminRequired is UNKNOWN rather than YES or NO.

Namespace scoping is not relevant from the supplied patch. SPI devices and DMA mapping ownership are not shown to be controllable through attacker-created namespaces. NamespaceScopedPrivilege=NO.

Prior setup exists in the practical sense that an SPI controller/device and DMA-capable transfer path must be present, but this is not scored as a rare hardware penalty. SPI is hardware-specific, but the prompt does not establish rare or physical-only attacker requirements. No network trigger is supported.

4. Primitive and severity interpretation

The exact primitive is a DMA mapping ownership and unwind inconsistency. The old code updated cur_tx_dma_dev and cur_rx_dma_dev only after all transfers were mapped. On partial failure, already-created mappings and per-transfer mapped flags could remain inconsistent with the recorded owner devices.

This is not a demonstrated heap UAF. It is also not merely passive bookkeeping, because later spi_unmap_msg may actively call DMA unmap code using a NULL or stale device or may release the same DMA mapping twice.

PrimitiveClass=CLASS_B because a real kernel ownership/lifetime-management primitive exists in DMA mapping state, but controlled reclaim, arbitrary read/write, callback control, or demonstrated LPE is not established.

The demonstrated consequence is kernel oops / DoS through NULL device dereference. The speculative consequence is limited DMA ownership or IOMMU state corruption from stale-device or double-unmap behavior. That unresolved device-memory ownership aspect justifies Actionable Moderate and required manual review, but not a Strong Important score.

ImportantCandidate=NO because the patch does not establish controlled memory corruption, privilege escalation, security-boundary bypass, or a strong exploitation primitive. AutoDowngradeAllowed=NO because treating this as an ordinary crash-only NULL dereference would discard the unresolved DMA ownership and double-unmap aspect.

5. One-sentence report phrase

A partial DMA mapping failure in the SPI core can leave DMA owner devices and per-transfer mapping flags inconsistent, allowing later cleanup to unmap with a NULL or stale device or double-unmap a mapping, causing a local kernel oops and requiring manual review due to unresolved DMA ownership risk.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is not only a NULL dereference. The patch establishes stale DMA owner state and possible double unmap of DMA mappings, which is an ownership primitive that should not be automatically closed as ordinary DoS without subsystem review.

7. Call-site confidence

Call-site confidence: medium

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

Patch: spi: Fix DMA mapping ownership on partial map failure
Commit: cc8354213ad6bd5fb8cc05a3fa3701188d086626
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cc8354213ad6bd5fb8cc05a3fa3701188d086626

Commit description:

If RX mapping fails after TX mapping succeeds, __spi_map_msg() unmaps
TX but leaves tx_sg_mapped set. If TX mapping fails on a later
transfer, mappings created for earlier transfers remain active.

In both cases, cur_{tx,rx}_dma_dev have not yet been updated because they
are assigned only after every transfer has been mapped. The subsequent
spi_unmap_msg() may therefore unmap the TX mapping again or release
earlier mappings using a NULL or stale device. Using a NULL device can
trigger an oops. An empty SG table does not prevent the NULL dereference
because dma_unmap_sg_attrs() accesses the device before checking the
entry count.

Publish both mapping devices before mapping starts and unwind all
failures through __spi_unmap_msg(). This clears the mapping flags and
releases each mapping once with the device that created it.

Publishing the devices before the loop also refreshes them when no
transfer needs mapping. No mapping flag is set in that case, so current
users do not use the pointers as mapping owners.

Fixes: e289df8 ("spi: Rework per message DMA mapped flag to be per transfer")
Cc: stable@vger.kernel.org
Signed-off-by: Honghui Jiang <jiang_hh2019@163.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://patch.msgid.link/20260814031419.43378-2-jiang_hh2019@163.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/spi/spi.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=cc8354213ad6bd5fb8cc05a3fa3701188d086626

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

The original Linux kernel CVE announcement for CVE-2026-90012 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90012

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:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 5.8

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: 4
  Paranoid ActionableScore: 5

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: MODERATE
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): MODERATE 7.0

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).