[CVE-2026-46304][MODERATE REGULAR] nvmet: avoid recursive nvmet-wq flush in nvmet_ctrl_free

[CVE-2026-46304][MODERATE REGULAR] nvmet: avoid recursive nvmet-wq flush in nvmet_ctrl_free

[AL-KERNEL]

CVE: CVE-2026-46304
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: nvmet: avoid recursive nvmet-wq flush in nvmet_ctrl_free
Commit: ae5b0cad163833e10b271e9becc05d81dae56e5f
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ae5b0cad163833e10b271e9becc05d81dae56e5f
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46304
Analysis date: Mon, 08 Jun 2026 14:45:44 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline, manual review recommended
Manual review required: YES

Summary:
A recursive workqueue flush in NVMe target controller teardown can be triggered during NVMe/TCP queue release, potentially stalling the nvmet workqueue and causing a network-adjacent denial of service.

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

The original Linux kernel CVE announcement for CVE-2026-46304 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46304

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.

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

CVE-2026-46304	MODERATE	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';CWE-667;*CWE-833;CWE-703;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.3';DESCR 'A recursive workqueue flush can occur in the NVMe target teardown path because nvmet_tcp_release_queue_work runs on nvmet-wq and can drop the final controller reference, leading nvmet_ctrl_free to flush ctrl async_event_work that is also queued on nvmet-wq. This can trigger a possible recursive locking warning and may stall controller teardown or the NVMe target workqueue under specific timing and lifecycle conditions. For the CVSS the PR:N is used for the paranoid score because a remote NVMe TCP initiator may be able to trigger controller and queue teardown without local privileges on the target, assuming access to the NVMe target endpoint. The issue is network adjacent rather than broadly Internet exposed in typical deployments because NVMe TCP targets are usually placed on isolated storage or data center networks. Impact is denial of service only, with no evidence of memory corruption, information disclosure, or privilege escalation from this patch context.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 4) 	MAYBE	LOCK DEADLOCK INIT WARNONLY NVME HARDWARE LINUS  INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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

ActionableScore=4
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 4
* Final recommended bucket: **Borderline, manual review recommended**

## 2. Signal breakdown

* Remote reachable / network-triggerable: +2
  NVMe/TCP controller and queue teardown can plausibly be triggered by an initiator connected to the NVMe/TCP target endpoint.

* Reliable kernel crash / strong DoS: +1
  The bug is a recursive `flush_work()` on the same `nvmet-wq`, producing a lockdep recursive locking warning and a plausible workqueue deadlock or teardown stall.

* Important filesystem/storage path: +1
  This affects NVMe target controller teardown, a storage service path.

* Hard or timing/lifecycle-specific condition: -1
  The issue requires a specific teardown path where `nvmet_tcp_release_queue_work()` drops the final controller reference while `async_event_work` is associated with the same workqueue.

* Paranoid-only availability impact: +1
  If the recursive flush turns into a real nvmet workqueue stall, it can disrupt the NVMe target service, not only produce a harmless warning.

* Not counted: memory corruption, UAF, double-free, OOB write, privilege escalation, confidentiality impact, integrity impact.
  The patch supports a synchronization / deadlock style DoS, not a memory corruption primitive.

## 3. Reachability analysis

A remote NVMe/TCP initiator may be able to influence controller and queue lifetime by connecting to and disconnecting from an exposed NVMe/TCP target. No local privileges on the target are required in that model, but the endpoint must already be configured and reachable. NVMe/TCP targets are not normally public Internet services and are usually deployed on storage or data-center networks, so this is network-adjacent exposure rather than broad remote exposure. Local namespaces or containers are not the main factor unless they can reach or operate the NVMe/TCP target endpoint.

## 4. Severity interpretation

This behaves like an actionable DoS-oriented storage networking bug, not an Important-class memory corruption vulnerability. The realistic impact is a controller teardown stall or NVMe target workqueue disruption. There is no evidence of attacker-controlled overwrite, stale object reuse, UAF reclaim, information disclosure, or privilege escalation. The paranoid score is higher only because the affected path is network-adjacent and service-impacting.

## 5. One-sentence report phrase

A recursive workqueue flush in NVMe target controller teardown can be triggered during NVMe/TCP queue release, potentially stalling the nvmet workqueue and causing a network-adjacent denial of service.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

This should not be auto-closed solely as a low-risk warning because it is in NVMe/TCP target code and may be triggerable by a connected initiator, but the lack of memory corruption or privilege-escalation evidence keeps it below Important.

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

Patch: nvmet: avoid recursive nvmet-wq flush in nvmet_ctrl_free
Commit: ae5b0cad163833e10b271e9becc05d81dae56e5f
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ae5b0cad163833e10b271e9becc05d81dae56e5f

Commit description:

nvmet_tcp_release_queue_work() runs on nvmet-wq and can drop the
final controller reference through nvmet_cq_put(). If that triggers
nvmet_ctrl_free(), the teardown path flushes ctrl->async_event_work on
the same nvmet-wq.

Call chain:

 nvmet_tcp_schedule_release_queue()
   kref_put(&queue->kref, nvmet_tcp_release_queue)
     nvmet_tcp_release_queue()
       queue_work(nvmet_wq, &queue->release_work) <--- nvmet_wq
         process_one_work()
           nvmet_tcp_release_queue_work()
             nvmet_cq_put(&queue->nvme_cq)
               nvmet_cq_destroy()
                 nvmet_ctrl_put(cq->ctrl)
                   nvmet_ctrl_free()
                     flush_work(&ctrl->async_event_work) <--- nvmet_wq

                      Previously Scheduled by :-
		        nvmet_add_async_event
		          queue_work(nvmet_wq, &ctrl->async_event_work);

This trips lockdep with a possible recursive locking warning.

[ 5223.015876] run blktests nvme/003 at 2026-04-07 20:53:55
[ 5223.061801] loop0: detected capacity change from 0 to 2097152
[ 5223.072206] nvmet: adding nsid 1 to subsystem blktests-subsystem-1
[ 5223.088368] nvmet_tcp: enabling port 0 (127.0.0.1:4420)
[ 5223.126086] nvmet: Created discovery controller 1 for subsystem nqn.2014-08.org.nvmexpress.discovery for NQN nqn.2014-08.org.nvmexpress:uuid:0f01fb42-9f7f-4856-b0b3-51e60b8de349.
[ 5223.128453] nvme nvme1: new ctrl: NQN "nqn.2014-08.org.nvmexpress.discovery", addr 127.0.0.1:4420, hostnqn: nqn.2014-08.org.nvmexpress:uuid:0f01fb42-9f7f-4856-b0b3-51e60b8de349
[ 5233.199447] nvme nvme1: Removing ctrl: NQN "nqn.2014-08.org.nvmexpress.discovery"

[ 5233.227718] ============================================
[ 5233.231283] WARNING: possible recursive locking detected
[ 5233.234696] 7.0.0-rc3nvme+ #20 Tainted: G           O     N
[ 5233.238434] --------------------------------------------
[ 5233.241852] kworker/u192:6/2413 is trying to acquire lock:
[ 5233.245429] ffff888111632548 ((wq_completion)nvmet-wq){+.+.}-{0:0}, at: touch_wq_lockdep_map+0x26/0x90
[ 5233.251438]
               but task is already holding lock:
[ 5233.255254] ffff888111632548 ((wq_completion)nvmet-wq){+.+.}-{0:0}, at: process_one_work+0x5cc/0x6e0
[ 5233.261125]
               other info that might help us debug this:
[ 5233.265333]  Possible unsafe locking scenario:

[ 5233.269217]        CPU0
[ 5233.270795]        ----
[ 5233.272436]   lock((wq_completion)nvmet-wq);
[ 5233.275241]   lock((wq_completion)nvmet-wq);
[ 5233.278020]
                *** DEADLOCK ***

[ 5233.281793]  May be due to missing lock nesting notation

[ 5233.286195] 3 locks held by kworker/u192:6/2413:
[ 5233.289192]  #0: ffff888111632548 ((wq_completion)nvmet-wq){+.+.}-{0:0}, at: process_one_work+0x5cc/0x6e0
[ 5233.294569]  #1: ffffc9000e2a7e40 ((work_completion)(&queue->release_work)){+.+.}-{0:0}, at: process_one_work+0x1c5/0x6e0
[ 5233.300128]  #2: ffffffff82d7dc40 (rcu_read_lock){....}-{1:3}, at: __flush_work+0x62/0x530
[ 5233.304290]
               stack backtrace:
[ 5233.306520] CPU: 4 UID: 0 PID: 2413 Comm: kworker/u192:6 Tainted: G           O     N  7.0.0-rc3nvme+ #20 PREEMPT(full)
[ 5233.306524] Tainted: [O]=OOT_MODULE, [N]=TEST
[ 5233.306525] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.17.0-0-gb52ca86e094d-prebuilt.qemu.org 04/01/2014
[ 5233.306527] Workqueue: nvmet-wq nvmet_tcp_release_queue_work [nvmet_tcp]
[ 5233.306532] Call Trace:
[ 5233.306534]  <TASK>
[ 5233.306536]  dump_stack_lvl+0x73/0xb0
[ 5233.306552]  print_deadlock_bug+0x225/0x2f0
[ 5233.306556]  __lock_acquire+0x13f0/0x2290
[ 5233.306563]  lock_acquire+0xd0/0x300
[ 5233.306565]  ? touch_wq_lockdep_map+0x26/0x90
[ 5233.306571]  ? __flush_work+0x20b/0x530
[ 5233.306573]  ? touch_wq_lockdep_map+0x26/0x90
[ 5233.306577]  touch_wq_lockdep_map+0x3b/0x90
[ 5233.306580]  ? touch_wq_lockdep_map+0x26/0x90
[ 5233.306583]  ? __flush_work+0x20b/0x530
[ 5233.306585]  __flush_work+0x268/0x530
[ 5233.306588]  ? __pfx_wq_barrier_func+0x10/0x10
[ 5233.306594]  ? xen_error_entry+0x30/0x60

[Commit description truncated; see the upstream URL below]

Changed files:
  drivers/nvme/target/core.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=ae5b0cad163833e10b271e9becc05d81dae56e5f

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

The original Linux kernel CVE announcement for CVE-2026-46304 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46304

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:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.3

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: 3
  Paranoid ActionableScore: 4

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).