[CVE-2025-40261][MODERATE 7.0] nvme: nvme-fc: Ensure ->ioerr_work is cancelled in nvme_fc_delete_ctrl()

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

CVE: CVE-2025-40261
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: nvme: nvme-fc: Ensure ->ioerr_work is cancelled in nvme_fc_delete_ctrl()
Commit: 33f64600a12055219bda38b55320c62cdeda9167
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=33f64600a12055219bda38b55320c62cdeda9167
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2025-40261
Analysis date: Wed, 09 Sep 2026 02:38:45 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2025-40261 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2025-40261

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-2025-40261	MODERATE	https://www.kernelcve.org/list/?q=CVE-2025-40261 CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H';*CWE-416;CWE-362;CWE-667;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.4';DESCR 'A race in the NVMe FC controller delete path can allow ioerr_work to be queued after cancel_work_sync has already returned. If the nvme_fc_ctrl object is then freed while the work item is still queued or running, the workqueue can operate on stale memory and trigger list corruption or a kernel BUG. For the CVSS the PR:N is used for the paranoid network adjacent model because a malicious or faulty FC target or fabric endpoint may provoke I/O errors without needing a local account on the host. The attack is not Internet remote and requires access to the Fibre Channel storage fabric or a trusted storage path. Impact is at least denial of service via kernel crash. In the paranoid case, limited confidentiality or integrity impact is kept because the bug has a plausible use after free and list corruption pattern, but no clear arbitrary write primitive is shown.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) 	MAYBE	DANGER NVME HARDWARE DEBUGFS LINUS KPANIC 	-	-	checked

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

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

1. ActionableScore

* Raw conservative score: 4
* Conservative score: 4
* Raw paranoid score: 5
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

No floor or cap changed the score.

2. Signal breakdown

Conservative signals:

* +2 Real UAF / lifetime violation: `ioerr_work` can be queued after `cancel_work_sync()` has returned, and the owning `nvme_fc_ctrl` object may later be freed while the work item is still queued or running.
* +1 Reliable kernel crash / strong DoS: the supplied trace shows workqueue list corruption followed by `kernel BUG` / Oops.
* +1 Firmware/storage-fabric mediated external influence: an NVMe-FC target, FC fabric condition, or I/O error source may influence the error path that queues `ioerr_work`, but this is not direct Internet-style network reachability.

Paranoid additional signal:

* +1 Weak unresolved exploitation concern: the stale object is an active embedded `work_struct` inside `nvme_fc_ctrl`, and workqueue list handling or callback execution may consume freed storage. This is stronger than a plain NULL dereference, but still below controlled reclaim or arbitrary write.

Important non-awarded signals:

* +2 direct remote/network reachable was not awarded because NVMe-FC is fabric/storage-path mediated, not ordinary IP remote exposure.
* Local unprivileged trigger was not awarded because the complete trigger chain below host admin is not established.
* Host-admin penalty was not applied because host-admin-equivalent privilege is not positively established for the complete failure sequence.
* Hard race penalty was not applied because the patch establishes an ordering bug, but not a narrow one-shot race that is clearly attacker-uncontrollable.
* Controlled reclaim is not demonstrated.
* Arbitrary or directed kernel write is not demonstrated.
* Confidentiality and integrity points are not awarded in the conservative score.
* Extra Availability is not awarded because the same crash is already counted once.
* Concrete repeated release/refcount was not awarded. There is no visible first release followed by a second lifetime/refcount mutation on the exact same dangling reference.
* Structured stale-object leverage as a stronger independent signal was not awarded beyond the paranoid weak concern because attacker-controlled replacement contents or callback control are not shown.

Repeated-release/refcount checklist:

* First release can end lifetime: not the relevant pattern here.
* Exact same reference survives to a second release: not established.
* Second operation mutates lifetime/refcount: not established.
* Dedicated +1 Concrete repeated release/refcount: not awarded.
* Paranoid repeated-refcount leverage +1: not awarded.
* FLOOR 5 from repeated-release rules: not applied.

3. Reachability analysis

The most plausible external actor is a malicious, faulty, or compromised NVMe-FC target or FC fabric endpoint that can provoke I/O errors while the host is deleting or tearing down the controller association. The full trigger is not proven to be guest-like or ordinary remote-only, because `nvme_fc_delete_ctrl()` is a host controller teardown path and may require local management activity, transport failure handling, or prior configured NVMe-FC connectivity.

HostAdminRequired is therefore UNKNOWN. The evidence does not prove that host admin is required, but it also does not prove a complete below-host-admin trigger. NamespaceScopedPrivilege is NO because no namespace-scoped capability path is involved. Prior setup exists in practice: the host must have an NVMe-FC controller and FC storage path configured. This is specialized storage fabric exposure, but I did not apply a rare-hardware penalty because the supplied evidence does not establish that the affected deployment is rare or physical-only in the scoring sense.

Race repeatability is partially controllable through I/O error and teardown timing, but the patch does not prove a very narrow or unreproducible timing window. No race penalty is applied.

4. Primitive and severity interpretation

The exact primitive is an async work lifetime violation: `ioerr_work` may remain queued or become queued after it was cancelled, and then the enclosing `nvme_fc_ctrl` object can be freed. The stale storage is an active structured kernel object, because an embedded work item participates in workqueue list management and may lead into callback execution. This is not fixed stale DMA storage.

The demonstrated consequence is list corruption and kernel crash. The speculative consequence is broader post-free corruption if freed storage is reused before the workqueue consumes it, but controlled reclaim, attacker-shaped replacement contents, function-pointer control, or arbitrary read/write are not established. Therefore this is CLASS_B, not CLASS_A.

ImportantCandidate is YES because this is a real active-object UAF in a storage transport teardown path with unresolved post-lifetime workqueue behavior. AutoDowngradeAllowed is NO because automatically treating it as ordinary crash-only DoS would discard a concrete lifetime corruption primitive that needs manual review. Likely operational severity is Actionable Moderate, with Important review justified but not proven Important-class exploitation.

5. One-sentence report phrase

An NVMe FC controller teardown race can leave `ioerr_work` queued or running after `nvme_fc_ctrl` is freed, causing workqueue list corruption and a kernel crash, with manual review needed because the stale work item is an active kernel object even though controlled reclaim or arbitrary write is not demonstrated.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: real async work UAF and list corruption are established, and the stale object is active workqueue state. The current evidence supports DoS, but post-free workqueue behavior should be reviewed before automatic downgrade.

7. Call-site confidence

Call-site confidence: medium

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

Patch: nvme: nvme-fc: Ensure ->ioerr_work is cancelled in nvme_fc_delete_ctrl()
Commit: 33f64600a12055219bda38b55320c62cdeda9167
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=33f64600a12055219bda38b55320c62cdeda9167

Commit description:

nvme_fc_delete_assocation() waits for pending I/O to complete before
returning, and an error can cause ->ioerr_work to be queued after
cancel_work_sync() had been called.  Move the call to cancel_work_sync() to
be after nvme_fc_delete_association() to ensure ->ioerr_work is not running
when the nvme_fc_ctrl object is freed.  Otherwise the following can occur:

[ 1135.911754] list_del corruption, ff2d24c8093f31f8->next is NULL
[ 1135.917705] ------------[ cut here ]------------
[ 1135.922336] kernel BUG at lib/list_debug.c:52!
[ 1135.926784] Oops: invalid opcode: 0000 [#1] SMP NOPTI
[ 1135.931851] CPU: 48 UID: 0 PID: 726 Comm: kworker/u449:23 Kdump: loaded Not tainted 6.12.0 #1 PREEMPT(voluntary)
[ 1135.943490] Hardware name: Dell Inc. PowerEdge R660/0HGTK9, BIOS 2.5.4 01/16/2025
[ 1135.950969] Workqueue:  0x0 (nvme-wq)
[ 1135.954673] RIP: 0010:__list_del_entry_valid_or_report.cold+0xf/0x6f
[ 1135.961041] Code: c7 c7 98 68 72 94 e8 26 45 fe ff 0f 0b 48 c7 c7 70 68 72 94 e8 18 45 fe ff 0f 0b 48 89 fe 48 c7 c7 80 69 72 94 e8 07 45 fe ff <0f> 0b 48 89 d1 48 c7 c7 a0 6a 72 94 48 89 c2 e8 f3 44 fe ff 0f 0b
[ 1135.979788] RSP: 0018:ff579b19482d3e50 EFLAGS: 00010046
[ 1135.985015] RAX: 0000000000000033 RBX: ff2d24c8093f31f0 RCX: 0000000000000000
[ 1135.992148] RDX: 0000000000000000 RSI: ff2d24d6bfa1d0c0 RDI: ff2d24d6bfa1d0c0
[ 1135.999278] RBP: ff2d24c8093f31f8 R08: 0000000000000000 R09: ffffffff951e2b08
[ 1136.006413] R10: ffffffff95122ac8 R11: 0000000000000003 R12: ff2d24c78697c100
[ 1136.013546] R13: fffffffffffffff8 R14: 0000000000000000 R15: ff2d24c78697c0c0
[ 1136.020677] FS:  0000000000000000(0000) GS:ff2d24d6bfa00000(0000) knlGS:0000000000000000
[ 1136.028765] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 1136.034510] CR2: 00007fd207f90b80 CR3: 000000163ea22003 CR4: 0000000000f73ef0
[ 1136.041641] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 1136.048776] DR3: 0000000000000000 DR6: 00000000fffe07f0 DR7: 0000000000000400
[ 1136.055910] PKRU: 55555554
[ 1136.058623] Call Trace:
[ 1136.061074]  <TASK>
[ 1136.063179]  ? show_trace_log_lvl+0x1b0/0x2f0
[ 1136.067540]  ? show_trace_log_lvl+0x1b0/0x2f0
[ 1136.071898]  ? move_linked_works+0x4a/0xa0
[ 1136.075998]  ? __list_del_entry_valid_or_report.cold+0xf/0x6f
[ 1136.081744]  ? __die_body.cold+0x8/0x12
[ 1136.085584]  ? die+0x2e/0x50
[ 1136.088469]  ? do_trap+0xca/0x110
[ 1136.091789]  ? do_error_trap+0x65/0x80
[ 1136.095543]  ? __list_del_entry_valid_or_report.cold+0xf/0x6f
[ 1136.101289]  ? exc_invalid_op+0x50/0x70
[ 1136.105127]  ? __list_del_entry_valid_or_report.cold+0xf/0x6f
[ 1136.110874]  ? asm_exc_invalid_op+0x1a/0x20
[ 1136.115059]  ? __list_del_entry_valid_or_report.cold+0xf/0x6f
[ 1136.120806]  move_linked_works+0x4a/0xa0
[ 1136.124733]  worker_thread+0x216/0x3a0
[ 1136.128485]  ? __pfx_worker_thread+0x10/0x10
[ 1136.132758]  kthread+0xfa/0x240
[ 1136.135904]  ? __pfx_kthread+0x10/0x10
[ 1136.139657]  ret_from_fork+0x31/0x50
[ 1136.143236]  ? __pfx_kthread+0x10/0x10
[ 1136.146988]  ret_from_fork_asm+0x1a/0x30
[ 1136.150915]  </TASK>

Fixes: 19fce04 ("nvme-fc: avoid calling _nvme_fc_abort_outstanding_ios from interrupt context")
Cc: stable@vger.kernel.org
Tested-by: Marco Patalano <mpatalan@redhat.com>
Reviewed-by: Justin Tee <justin.tee@broadcom.com>
Signed-off-by: Ewan D. Milne <emilne@redhat.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  lib/list_debug.c
  drivers/nvme/host/fc.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=33f64600a12055219bda38b55320c62cdeda9167

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

The original Linux kernel CVE announcement for CVE-2025-40261 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2025-40261

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:H
  The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 6.4

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).