[CVE-2026-80589][MODERATE 7.0] block: stop the timeout timer when releasing a never added disk [ Upstream

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

CVE: CVE-2026-80589
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: block: stop the timeout timer when releasing a never added disk [ Upstream
Commit: 6ae7364f68e6c7af6b6df4bbb14040b89e5975d0
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6ae7364f68e6c7af6b6df4bbb14040b89e5975d0
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80589
Analysis date: Wed, 26 Aug 2026 12:37:37 -0400
ActionableScore: 7
ActionableScore lower bound: 5
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A block-layer lifetime bug can leave an mq request_queue timeout timer armed after a never-added disk is released, causing a use-after-free in timer or blk_mq timeout handling and leading to a kernel crash, with limited but nonzero concern for stronger memory-corruption impact in device-controlled or virtualized storage environments.

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

The original Linux kernel CVE announcement for CVE-2026-80589 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80589

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-2026-80589	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	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-672;*CWE-664;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A use-after-free can occur in the block layer when disk_release() handles a probe failure for a disk that was never added. If I/O was issued before add_disk(), the request_queue timeout timer can remain armed after the queue is freed and later timer handling may write through the dangling timer entry. This is primarily a local high complexity trigger involving failed device probe or reset paths, observed through NVMe namespace setup and KASAN splats in timer and blk_mq timeout code. For the CVSS the PR:L is used for the paranoid score because an unprivileged or reduced privilege local actor may be able to influence reset or reprobe flows in some deployments, although reliable triggering often needs device control or a faulty or malicious controller. The issue is not a generic remote network bug, but storage fabrics or virtualized device models can expand the practical attack surface. Impact is at least denial of service via kernel crash and in the paranoid interpretation may include confidentiality and integrity impact due to use-after-free memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7)	YES	INIT LEAK UAF TIMER HARDWARE TEST  KPANIC INCREASED_TO_MODERATE7_BASED_ON_GUESSCVSS KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN6 DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
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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:

* Firmware-mediated external influence: +1. NVMe controller behavior, reset timing, namespace probing, and device_add_disk failure can influence the vulnerable path.
* Memory corruption, Strong corruption primitive: +2. The report shows a real slab-use-after-free involving a freed request_queue still linked into the timer wheel.
* Real lifetime corruption: +1. q->timeout and queue work can survive past queue teardown.
* Reliable kernel crash / strong DoS: +1. KASAN reports UAF in timer deletion and other runs hit enqueue_timer(), __run_timers(), or blk_mq_timeout_work().
* Privileged kernel/device-management memory corruption path: +1. The bug is in block/NVMe probe and reset handling.
* Important filesystem/storage path: +1. The block layer and NVMe namespace setup are important storage infrastructure.
* Hard or special timing/failure condition: -1. Triggering requires a never-added disk plus I/O before add_disk() and a later probe/reset/failure path.
* Constrained or kernel-derived corruption: -1. The observed write is timer/list metadata manipulation, not an attacker-chosen arbitrary write.

Paranoid additions:

* Local reduced-privilege trigger possibility: +1. In virtualized, storage-fabric, fuzzing, or delegated device-management environments, a less-than-full-root actor may influence reset or reprobe behavior.
* Availability impact realistic: +1. The failure is host-kernel level and can crash or destabilize the system, not just fail one I/O operation.

Not awarded:

* Strong LPE plausibility: +0. The patch shows UAF/write-after-free, but not attacker-controlled reclaim, object replacement, callback control, or arbitrary write.
* Remote reachable: +0. This is not a generic network-triggerable path.

Call-site confidence: high. The commit message provides the relevant disk_release(), blk_sync_queue(), nvme_reset_work(), and timer call path.

## 3. Reachability analysis

The most realistic trigger involves NVMe namespace probing or reset where I/O is issued before add_disk(), followed by a failure path that releases the disk while the queue timeout timer remains armed. A normal local user usually cannot reliably force this on bare metal without device-management privileges or a faulty or malicious controller. However, firmware, virtualized NVMe devices, storage fabrics, or reduced-privilege management contexts can expand practical reachability. Containers and namespaces do not automatically make this reachable, but delegated device or storage management could lower the practical privilege requirement.

## 4. Severity interpretation

This is more than an ordinary Moderate because the patch fixes a concrete lifetime UAF in a core storage path, with KASAN evidence and multiple timer/workqueue crash sites. Realistically, the demonstrated impact is kernel crash or host instability. Privilege escalation is not proven, but the UAF occurs in trusted block-layer timer/list handling, so the paranoid score should keep it in manual-review territory rather than auto-closing it as a simple DoS.

## 5. One-sentence report phrase

A block-layer lifetime bug can leave an mq request_queue timeout timer armed after a never-added disk is released, causing a use-after-free in timer or blk_mq timeout handling and leading to a kernel crash, with limited but nonzero concern for stronger memory-corruption impact in device-controlled or virtualized storage environments.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED.

Reason: this is a concrete UAF in a core block/NVMe lifetime path with write-after-free evidence, not just a warning or resource leak.

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

Patch: block: stop the timeout timer when releasing a never added disk [ Upstream
Commit: 6ae7364f68e6c7af6b6df4bbb14040b89e5975d0
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6ae7364f68e6c7af6b6df4bbb14040b89e5975d0

Changed files:
  kernel/time/timer.c
  block/blk-core.c
  drivers/nvme/host/core.c
  drivers/nvme/host/pci.c
  block/blk-mq.c
  kernel/rcu/tree.c
  block/genhd.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=6ae7364f68e6c7af6b6df4bbb14040b89e5975d0

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

The original Linux kernel CVE announcement for CVE-2026-80589 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80589

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: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: 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).