[CVE-2026-72375][MODERATE 7.0] afs: Fix reinitialisation of the inode, in particular ->lock_work [ Upstream

[CVE-2026-72375][MODERATE 7.0] afs: Fix reinitialisation of the inode, in particular ->lock_work [ Upstream

[AL-KERNEL]

CVE: CVE-2026-72375
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: afs: Fix reinitialisation of the inode, in particular ->lock_work [ Upstream
Commit: 63d3f283858fae097fb09ddd4ce46bb0bc1f9d01
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=63d3f283858fae097fb09ddd4ce46bb0bc1f9d01
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72375
Analysis date: Sun, 16 Aug 2026 03:06:36 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: NO

Summary:
AFS delayed lock_work was not reinitialized per allocated inode and was not flushed during inode eviction, creating a local workqueue lifetime race that can trigger DEBUG_OBJECTS warnings and may represent a UAF class issue on systems with accessible AFS mounts.

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

The original Linux kernel CVE announcement for CVE-2026-72375 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72375

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: NO

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-2026-72375	MODERATE	CHECK WITH IMPACT FROM ORIG NN NONE	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-362;*CWE-672;CWE-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'AFS lock_work was initialized only once for the slab object instead of being reinitialized for each newly allocated inode, and the delayed work was not flushed when the inode was evicted. This creates a workqueue lifetime race where afs_lock_work may be queued or still running while the owning vnode and inode are being destroyed or reused, which is a plausible UAF class issue rather than a simple warning only bug. For the CVSS the PR:L is used because a local user who can access an AFS mount and perform file locking operations may be able to reach the affected path without full administrator privileges. The issue is not directly network reachable because triggering depends on local filesystem operations on the client. Impact is at least a local denial of service via warning or kernel crash and in the paranoid case may allow confidentiality and integrity impact due to memory corruption through UAF.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	READ LOCK DANGER DISK INIT SKIP HARDWARE LINUS  INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP	NO	NO	checked

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

ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Triggered signals:

* Local unprivileged trigger: +1
  A local user with access to an AFS mount may trigger the affected path through file locking operations such as fcntl setlk.

* Memory corruption, weak or indirect corruption candidate: +1
  The patch concerns a work_struct embedded in an inode object whose initialization and lifetime were incorrect. This is stronger than pure bookkeeping, but the patch does not show attacker controlled reclaim or overwrite.

* Real lifetime corruption: +1
  Moving INIT_DELAYED_WORK from slab init to per inode allocation and adding flush_delayed_work during eviction indicates a real object lifetime issue involving delayed work and inode teardown.

* Reliable kernel warning or possible crash concern: +1
  The observed failure is an ODEBUG warning during work activation. A production crash is not directly demonstrated, but workqueue lifetime bugs can plausibly become kernel warning, Oops, or panic depending on debug and panic_on_warn settings.

* Weak LPE concern in paranoid scoring: +1
  The stale delayed work callback operates on an inode backed vnode object. This gives a plausible UAF style concern, but no controlled reclaim, type confusion, arbitrary write, or exploit primitive is demonstrated.

Negative or limiting signals:

* Hard or unreliable timing condition: -1
  The warning is occasional and tied to inode reuse, delayed work state, and eviction timing.

* Rare or configuration dependent exposure: -1 in conservative interpretation
  AFS is not a default filesystem for most Linux installations and practical triggering requires an AFS mount.

Conservative total is 4. Paranoid total is 5 by keeping the lifetime UAF concern and weak LPE concern for manual triage sensitivity.

## 3. Reachability analysis

The bug is locally reachable on systems using AFS where an attacker can access files on an AFS mount and exercise POSIX file locking. It is not directly network reachable from a remote host in the CVSS sense, even though AFS itself is a network filesystem. The trigger is client side filesystem activity, not unauthenticated packet parsing.

Privileges are likely PR:L rather than PR:H when an AFS mount already exists and is accessible to local users. Mounting or configuring AFS may require administrator action, but using an existing mount and issuing file lock operations does not necessarily require full administrative privileges. Containers and namespaces do not automatically make this reachable unless the AFS mount is exposed inside the container.

## 4. Severity interpretation

This behaves more like an actionable Moderate than an ordinary low risk warning. The demonstrated symptom is a DEBUG_OBJECTS warning, but the fix addresses delayed work reinitialization and flushing during inode eviction, which are classic lifetime safety points.

Theoretical impact includes UAF style memory corruption if lock_work runs after the inode or vnode lifetime has ended or after the object has been reused. Realistic exploitation evidence is limited because the patch does not show attacker controlled reclaim, object replacement, arbitrary write, or callback target control. Therefore this should not be treated as a strong Important by default, but it should not be auto closed either.

## 5. One-sentence report phrase

AFS delayed lock_work was not reinitialized per allocated inode and was not flushed during inode eviction, creating a local workqueue lifetime race that can trigger DEBUG_OBJECTS warnings and may represent a UAF class issue on systems with accessible AFS mounts.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: the patch fixes an embedded delayed work lifetime problem in inode teardown and allocation paths. The demonstrated failure is only a warning, but the bug class is close enough to UAF that a reviewer should inspect afs_lock_work lifetime, inode reuse, and whether any stale callback can access freed or attacker influenced vnode state.

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

Patch: afs: Fix reinitialisation of the inode, in particular ->lock_work [ Upstream
Commit: 63d3f283858fae097fb09ddd4ce46bb0bc1f9d01
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=63d3f283858fae097fb09ddd4ce46bb0bc1f9d01

Changed files:
  lib/debugobjects.c
  fs/afs/inode.c
  fs/afs/super.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=63d3f283858fae097fb09ddd4ce46bb0bc1f9d01

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

The original Linux kernel CVE announcement for CVE-2026-72375 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72375

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:L/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: 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: NO
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).