[CVE-2026-72146][MODERATE REGULAR] dmaengine: sh: rz-dmac: Move interrupt request after everything is set up

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

CVE: CVE-2026-72146
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: dmaengine: sh: rz-dmac: Move interrupt request after everything is set up
Commit: 5b12de6229d662864ee22c11d4876652b40120f0
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5b12de6229d662864ee22c11d4876652b40120f0
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72146
Analysis date: Sat, 15 Aug 2026 21:15:45 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Borderline. Manual review recommended
Manual review required: YES

Summary:
An initialization ordering race in the RZ DMAC driver can allow an IRQ handler or IRQ thread to access uninitialized channel state during probe, leading primarily to a local hardware-specific kernel crash.

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

The original Linux kernel CVE announcement for CVE-2026-72146 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72146

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 REGULAR
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-2026-72146	MODERATE	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-362;CWE-665;CWE-908;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'An initialization ordering race exists in the RZ DMAC driver because channel IRQs could be requested before channel ch_base and descriptor list state were fully initialized. Once devm_request_threaded_irq succeeds, the IRQ handler or IRQ thread may run immediately and access non initialized channel state such as ch_base, ld_free, ld_queue, or ld_active. This can lead to invalid memory access in interrupt context and a kernel crash. For the CVSS the PR:L is used for the paranoid score because reliable triggering normally needs local code execution with delegated driver bind, reset, or device management capability, while a standard deployment usually requires administrator level control and fits PR:H for the base score. The issue is not network reachable and requires the affected Renesas RZ DMAC hardware and driver probe or re probe path. Impact is at least local denial of service. In worst case, limited confidentiality or integrity impact is kept for manual review because the IRQ thread can touch uninitialized list state, but no clear arbitrary write primitive is shown.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline. Manual review recommended (with actual score 3)  SKIP CVE-2026-72146 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	OOB INIT PRINTF-TTY NOMEMCHK ERRORPATH DMAorINTERRUPT HARDWARE LINUS MEMORY  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=3
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 3
* Final recommended bucket: **Borderline. Manual review recommended**::

## 2. Signal breakdown

Triggered signals:

* Weak/indirect corruption candidate: +1
  The IRQ handler may access `channel->ch_base` before initialization, and the IRQ thread may touch uninitialized list heads such as `ld_free`, `ld_queue`, and `ld_active`.

* Reliable kernel crash / strong DoS: +1
  Invalid memory access from IRQ or threaded IRQ context can realistically crash the kernel on affected hardware during probe or reprobe.

* Privileged kernel/device-management memory corruption path: +1
  The bug is in DMA driver initialization and IRQ setup, a trusted device-management path with weak attacker control but high kernel privilege.

* Firmware-mediated or hardware-mediated external influence: +1, paranoid only
  The immediate trigger is an IRQ that may fire after registration. This is not network reachable, but the interrupt timing can be influenced by device or hardware state.

Subtracted signals:

* Hard or timing-dependent race: -1
  The issue depends on an interrupt arriving in the narrow window after IRQ registration and before full channel initialization.

* Requires admin/root/device-management privileges in typical deployments: -2 conservative, -1 paranoid
  Normal triggering requires driver probe, bind, reset, or device-management control. Paranoid scoring uses a smaller penalty because some embedded or delegated service environments may expose reduced device-management control without full host-root equivalence.

* Hardware-specific condition: -1
  This affects the Renesas RZ/G2L DMAC driver path, not a broad default kernel subsystem.

Not awarded:

* No remote/network trigger.
* No strong LPE signal.
* No demonstrated UAF reclaim, arbitrary write, callback control, type confusion, or attacker-controlled object replacement.
* No confidentiality or integrity impact in the conservative score.

## 3. Reachability analysis

The realistic trigger is local and tied to the affected platform driver lifecycle. An attacker would typically need administrator-level ability to load, bind, unbind, reprobe, reset, or otherwise influence the RZ DMAC platform device. Ordinary local users normally cannot reach this path.

Namespaces and containers usually do not lower the requirement unless device-management operations are deliberately delegated into the container or service context. The issue is not reachable through network traffic. It requires affected Renesas RZ DMAC hardware and an interrupt arriving during the vulnerable initialization window.

Call-site confidence: high, because the patch shows the affected probe path, IRQ request placement, initialization order, and cleanup changes.

## 4. Severity interpretation

This behaves more like a hardware-specific Moderate driver initialization race than an Important-class vulnerability. The main practical impact is local kernel crash or boot/probe instability on affected systems.

The theoretical concern is that uninitialized list state can be accessed from IRQ thread context, which is more concerning than a simple NULL dereference. However, the patch does not show a strong exploitation primitive such as UAF reuse, controlled overwrite, function pointer control, arbitrary write, or type confusion. Therefore the paranoid score is only borderline actionable, not Important.

## 5. One-sentence report phrase

An initialization ordering race in the RZ DMAC driver can allow an IRQ handler or IRQ thread to access uninitialized channel state during probe, leading primarily to a local hardware-specific kernel crash.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Manual review is recommended because the bug involves an IRQ-time race and invalid access to uninitialized driver state, including list heads. It is not urgent Important-class based on the supplied patch because exploitation appears hardware-specific, local, timing-dependent, and normally requires privileged device-management access.

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

Patch: dmaengine: sh: rz-dmac: Move interrupt request after everything is set up
Commit: 5b12de6229d662864ee22c11d4876652b40120f0
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5b12de6229d662864ee22c11d4876652b40120f0

Commit description:

Once the interrupt is requested, the interrupt handler may run immediately.
Since the IRQ handler can access channel->ch_base, which is initialized
only after requesting the IRQ, this may lead to invalid memory access.
Likewise, the IRQ thread may access uninitialized data (the ld_free,
ld_queue, and ld_active lists), which may also lead to issues.

Request the interrupts only after everything is set up. To keep the error
path simpler, use dmam_alloc_coherent() instead of dma_alloc_coherent().

Fixes: 5000d37 ("dmaengine: sh: Add DMAC driver for RZ/G2L SoC")
Cc: stable@vger.kernel.org
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Tested-by: John Madieu <john.madieu.xa@bp.renesas.com>
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Tested-by: Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>
Link: https://patch.msgid.link/20260526084710.3491480-2-claudiu.beznea@kernel.org
[tm: Kept the channel->irq field in rz_dmac_chan_probe() instead of
 upstream's local `irq` variable, as commit 04e227718ab8
 ("dmaengine: sh: rz-dmac: Make channel irq local") is not present
 in this tree. Likewise kept platform_get_irq_byname() instead of
 platform_get_irq_byname_optional() for the error IRQ in rz_dmac_probe(),
 as commit 6b3a6b6dc074 ("dmaengine: sh: rz_dmac: make error interrupt
 optional") is not present in this tree either; its early return on
 failure becomes a goto err jump to match the new call order.]
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Changed files:
  drivers/dma/sh/rz-dmac.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=5b12de6229d662864ee22c11d4876652b40120f0

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

The original Linux kernel CVE announcement for CVE-2026-72146 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72146

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: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: 2
  Paranoid ActionableScore: 3

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: NO
Published priority for this report (same as in Subject): MODERATE REGULAR

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).