[CVE-2026-46005][LOW] xfs: fix a resource leak in xfs_alloc_buftarg() [ Upstream

[CVE-2026-46005][LOW] xfs: fix a resource leak in xfs_alloc_buftarg() [ Upstream

[AL-KERNEL]

CVE: CVE-2026-46005
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: xfs: fix a resource leak in xfs_alloc_buftarg() [ Upstream
Commit: 82fb9da6477d08bdab954dc7bc081a41f2f9cae6
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=82fb9da6477d08bdab954dc7bc081a41f2f9cae6
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46005
Analysis date: Wed, 27 May 2026 10:11:56 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A missing `fs_put_dax()` call in the XFS DAX setup error path can leak a DAX device reference after failed allocation, requiring privileged mount or device-management activity and causing resource-retention DoS only.

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

The original Linux kernel CVE announcement for CVE-2026-46005 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46005

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: LOW
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
======================================================================

CVE-2026-46005	LOW	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';*CWE-772;CWE-404;*CWE-401;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.1';DESCR 'A resource leak can occur in the XFS DAX setup error path because xfs_alloc_buftarg() frees the buffer target structure without dropping the DAX device reference. Repeated failed setup or mount attempts could leave stale DAX references and may prevent clean device release or cause resource exhaustion in affected configurations. For the CVSS the PR:H is used because triggering this path normally requires administrative mount or DAX device management privileges. The issue is not network reachable and does not involve a UAF, out of bounds access, arbitrary write, or privilege escalation primitive. Impact is denial of service or resource retention only, with no supported confidentiality or integrity impact.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 0)	YES	DISK SIMPLEFIX LEAK ERRORPATH HARDWARE LINUS 	YES	NO	checked

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

ActionableScore=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 0
* Final recommended bucket: **Ordinary Moderate / Low-like**::

## 2. Signal breakdown

Triggered signals:

* Important filesystem/storage path: +1
  The issue is in XFS buffer target allocation for DAX-related setup.

* Availability impact weakly plausible: +1
  Repeated failures could retain DAX device references and interfere with clean device release or resource cleanup.

Subtracting signals:

* Requires admin/root/CAP_SYS_ADMIN in typical deployments: -2
  Triggering normally requires privileged XFS mount/setup activity and access to DAX-capable storage.

* Rare/configuration-dependent path: -1
  The affected path requires XFS with DAX involvement and an error path in `xfs_alloc_buftarg()`.

No signals apply for remote reachability, local unprivileged trigger, memory corruption, UAF, OOB access, privilege escalation, sensitive-object access, or security-boundary bypass.

Net score is clamped to 0.

## 3. Reachability analysis

The bug is reachable through an XFS DAX setup or mount error path. A normal unprivileged local user cannot reliably trigger it in typical deployments because mounting filesystems and managing DAX devices requires administrative privileges.

Namespaces and containers generally do not reduce the requirement unless the container is granted powerful device and mount privileges. The path is not default-exposed to remote attackers and is not network-triggerable.

## 4. Severity interpretation

This behaves like a Low-like resource management bug rather than an actionable Moderate or Important issue. The patch fixes a missing `fs_put_dax()` reference drop, not a memory corruption primitive.

Theoretical impact is resource retention or DoS after repeated privileged failure paths. Realistic evidence supports only an admin-triggered reference leak with no confidentiality, integrity, or privilege-escalation impact.

## 5. One-sentence report phrase

A missing `fs_put_dax()` call in the XFS DAX setup error path can leak a DAX device reference after failed allocation, requiring privileged mount or device-management activity and causing resource-retention DoS only.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This is an admin-only XFS DAX reference leak with no memory corruption, no remote exposure, and no supported privilege-escalation primitive.

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

Patch: xfs: fix a resource leak in xfs_alloc_buftarg() [ Upstream
Commit: 82fb9da6477d08bdab954dc7bc081a41f2f9cae6
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=82fb9da6477d08bdab954dc7bc081a41f2f9cae6

Changed files:
  fs/xfs/xfs_buf.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=82fb9da6477d08bdab954dc7bc081a41f2f9cae6

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

The original Linux kernel CVE announcement for CVE-2026-46005 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46005

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:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.1

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: unknown
  Paranoid ActionableScore: 0

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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).