[CVE-2026-53062][MODERATE 7.0] dm cache policy smq: fix missing locks in invalidating cache blocks [ Upstream

[CVE-2026-53062][MODERATE 7.0] dm cache policy smq: fix missing locks in invalidating cache blocks [ Upstream

[AL-KERNEL]

CVE: CVE-2026-53062
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: dm cache policy smq: fix missing locks in invalidating cache blocks [ Upstream
Commit: 4991b5a08751e2e82488fb93ae08849b6aea10d9
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4991b5a08751e2e82488fb93ae08849b6aea10d9
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53062
Analysis date: Wed, 24 Jun 2026 13:20:11 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A race in dm-cache SMQ passthrough invalidation can let concurrent workers update and free shared cache policy entries without locking, causing metadata races and possible use-after-free in the block storage path.

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

The original Linux kernel CVE announcement for CVE-2026-53062 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53062

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-2026-53062	MODERATE	CHECK	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-362;CWE-667;*CWE-416;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A race condition in dm cache policy smq can occur because smq_invalidate_mapping() may run concurrently from multiple workers in passthrough mode without holding the policy lock. The affected path updates shared cache policy structures through queue removal, hash removal, and entry freeing, so concurrent writes can corrupt policy state and may lead to use after free of internal data structures. For the CVSS the PR:L is used for the paranoid score because a system may already expose a passthrough dm cache device where a local user or service can generate writes without being allowed to reconfigure device mapper itself. The issue is not network reachable by itself and requires local I/O to the affected dm cache mapping. Impact is at least local denial of service via kernel crash or metadata corruption, and in the worst case may allow confidentiality or integrity impact due to the UAF class. YES REQUIRES MANUAL CHECK';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	WRITE OOB LOCK DISK RACE UAF HARDWARE LINUS KPANIC  KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN7	NO	YES	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

* Local unprivileged trigger: +1 in the paranoid interpretation. If the dm-cache mapping is already configured in passthrough mode and exposed to a local user or service, concurrent writes may trigger invalidation without allowing that user to reconfigure device mapper.
* Generic memory corruption, weak primitive: +1. The commit explicitly mentions possible use-after-free of internal SMQ data structures, but the patch does not show attacker-controlled reclaim, controlled overwrite, callback dispatch, or type confusion.
* Real lifetime corruption: +1. `free_entry()` may race with concurrent `del_queue()` / `h_remove()` users of the same policy entry, which is a real object lifetime issue.
* Reliable kernel crash / strong DoS: +1. Concurrent invalidation can corrupt policy state and plausibly crash or destabilize the kernel storage path, although the provided reproducer mainly demonstrates inconsistent counters.
* Important filesystem/storage path: +1. This is in device-mapper cache policy code and can affect block I/O correctness and cache metadata behavior.
* Requires admin/CAP_SYS_ADMIN in typical deployments: -2 for the conservative score. Creating, suspending, reloading, and switching a dm-cache target into passthrough mode normally requires administrative privileges.
* Hard race / special timing: 0. Although this is a race, the commit gives a realistic concurrent-write reproducer using multiple workers, so I would not subtract the timing penalty.

## 3. Reachability analysis

The fully controlled reproducer requires `dmsetup` operations, so the conservative interpretation is a local administrative trigger. However, the actual vulnerable operation is concurrent write-driven invalidation in an already configured passthrough dm-cache device. In deployments where such a device is exposed to a less privileged local user, service, VM backend, or container workload through a filesystem or block interface, PR can effectively drop to local user level for triggering writes.

This is not network reachable by itself. Containers and namespaces usually do not provide direct host device-mapper control, but they may still issue I/O to an already exposed mapped device. The vulnerable mode is configuration-dependent, but it is not a legacy-only or purely hardware-specific path.

## 4. Severity interpretation

This is stronger than an ordinary Moderate resource bug because the patch and commit message explicitly identify missing locking around shared structure removal and freeing, with possible use-after-free. At the same time, the demonstrated primitive is weak: there is no shown attacker-controlled reclaim, arbitrary write, function pointer control, or reliable LPE path.

The conservative result is borderline/manual-review Moderate. The paranoid result is Actionable Moderate because a local write-only trigger against an already configured dm-cache device plus a real lifetime corruption candidate is enough to avoid auto-closing.

## 5. One-sentence report phrase

A race in dm-cache SMQ passthrough invalidation can let concurrent workers update and free shared cache policy entries without locking, causing metadata races and possible use-after-free in the block storage path.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

The issue involves a race-dependent UAF candidate in a storage subsystem. Practical privilege escalation is not demonstrated, but the lifetime corruption is explicit enough that it should not be auto-closed without manual review.

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

Patch: dm cache policy smq: fix missing locks in invalidating cache blocks [ Upstream
Commit: 4991b5a08751e2e82488fb93ae08849b6aea10d9
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4991b5a08751e2e82488fb93ae08849b6aea10d9

Changed files:
  drivers/md/dm-cache-policy-smq.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=4991b5a08751e2e82488fb93ae08849b6aea10d9

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

The original Linux kernel CVE announcement for CVE-2026-53062 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53062

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).