[CVE-2026-80698][MODERATE 7.0] dmaengine: idxd: fix double free of wq, engine, and group structs [ Upstream

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

CVE: CVE-2026-80698
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: dmaengine: idxd: fix double free of wq, engine, and group structs [ Upstream
Commit: c93a9f652b7373ac8ee5bfcc18a9af76959b6c6c
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c93a9f652b7373ac8ee5bfcc18a9af76959b6c6c
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80698
Analysis date: Fri, 28 Aug 2026 05:13:56 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum**:: Actionable Moderate at minimum. Strong Important candidate only if local low privilege triggering of idxd setup or cleanup error paths is practical in the evaluated environment.
Manual review required: YES

Summary:
A double free in the dmaengine idxd device setup and cleanup paths can occur because release callbacks and explicit cleanup code both free the same wq, engine, and group objects after put_device(), creating kernel heap corruption with realistic DoS impact and possible but unproven privilege escalation risk.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-80698 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80698

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-80698	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:H/I:H/A:H';CWE-415;*CWE-416;*CWE-664;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A double free can occur in the dmaengine idxd driver because wq, engine, and group objects are freed by their device release callbacks and were also freed explicitly by setup error paths or cleanup functions after put_device. When put_device drops the reference count to zero, the release callback owns the final free, so a later kfree operates on already freed kernel memory. For the CVSS the PR:L is used in the paranoid score because a local actor with limited but relevant control over driver lifecycle, device management, or resource pressure may be able to reach error or cleanup paths in some deployments. The realistic base case is closer to PR:H because normal idxd load and remove operations are administrator controlled. The issue is not network reachable. Impact is at least local denial of service via kernel memory corruption and in the worst case may allow confidentiality or integrity impact if the double free can be shaped into a usable kernel heap corruption primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5)	YES	INIT ERRORPATH UAF HARDWARE KPANIC MEMORY 	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: **4**
* Paranoid score: **5**
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: Actionable Moderate at minimum. Strong Important candidate only if local low privilege triggering of idxd setup or cleanup error paths is practical in the evaluated environment.

## 2. Signal breakdown

Triggered signals:

* **Memory corruption, Strong corruption primitive: +2**
  The patch fixes explicit double free of `wq`, `engine`, and `group` structs after `put_device()` may already invoke release callbacks that call `kfree()`.

* **Real lifetime corruption: +1**
  This is a device lifetime ownership bug involving `struct device` reference release callbacks and cleanup paths.

* **Privileged kernel/device-management memory corruption path: +1**
  The corruption occurs in a DMA engine driver setup and cleanup path, which is a trusted kernel device-management context.

* **Reliable kernel crash / strong DoS: +1**
  Double free in kernel heap cleanup paths can realistically lead to allocator corruption, warning, oops, or crash.

Subtracting signals:

* **Requires admin/root/CAP_* in typical deployments: -2**
  Normal triggering requires driver probe/remove, device lifecycle control, or setup failure paths for Intel idxd hardware, typically administrator controlled.

* **Rare AND difficult-to-reach subsystem/configuration: -1**
  Requires the idxd driver and suitable Intel DSA/IAA hardware or equivalent device setup path.

Paranoid adjustment:

* **Weak LPE concern: +1**
  Double free is a kernel heap corruption class. No reclaim or controlled replacement primitive is shown, so this is not strong LPE evidence, but it is enough to avoid auto-close.

## 3. Reachability analysis

The realistic trigger is local and privileged: device probing, removal, cleanup, or setup error unwinding in the `idxd` DMA engine driver. Typical users cannot directly reach these paths without administrative control over the device or driver lifecycle.

Namespaces and containers usually do not make this reachable unless device management, driver control, or relevant sysfs/device operations are delegated into the container. If a reduced-capability root, service account, or container root can influence idxd device lifecycle or resource pressure enough to force setup errors, PR:L is a defensible paranoid interpretation.

The path is not network reachable. It is hardware and driver dependent, so exposure is limited to systems with idxd-capable hardware and the driver enabled.

Call-site confidence: **high**, because the patch and commit message directly describe the release callbacks, `put_device()` behavior, and redundant `kfree()` calls in setup and cleanup paths.

## 4. Severity interpretation

This is not an ordinary Moderate resource leak or validation bug. It is a real kernel lifetime bug with double free behavior, but practical exploitation appears constrained by privileged device-management reachability and hardware specificity.

Realistically, it behaves like a local privileged kernel crash or allocator corruption issue. Theoretical privilege escalation cannot be excluded because double free is a memory corruption primitive, but the patch does not show attacker-controlled reclaim, object replacement, callback control, or arbitrary write.

Therefore the conservative result is borderline manual review, while the paranoid result is Actionable Moderate and should not be auto-closed.

## 5. One-sentence report phrase

A double free in the dmaengine idxd device setup and cleanup paths can occur because release callbacks and explicit cleanup code both free the same wq, engine, and group objects after put_device(), creating kernel heap corruption with realistic DoS impact and possible but unproven privilege escalation risk.

## 6. Manual review recommendation

**MANUAL CHECK REQUIRED**

Reason: this is a kernel double free in a DMA driver lifetime path. Even though normal triggering is likely privileged and hardware dependent, the memory corruption class and possible lower-privilege device-management deployments make it unsuitable for automatic closure.

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

Patch: dmaengine: idxd: fix double free of wq, engine, and group structs [ Upstream
Commit: c93a9f652b7373ac8ee5bfcc18a9af76959b6c6c
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c93a9f652b7373ac8ee5bfcc18a9af76959b6c6c

Changed files:
  drivers/dma/idxd/init.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=c93a9f652b7373ac8ee5bfcc18a9af76959b6c6c

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

The original Linux kernel CVE announcement for CVE-2026-80698 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80698

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: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: 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).