[CVE-2026-80529][MODERATE REGULAR] xfs: don't swallow dquot recovery verification errors

[CVE-2026-80529][MODERATE REGULAR] xfs: don't swallow dquot recovery verification errors

[AL-KERNEL]

CVE: CVE-2026-80529
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: xfs: don't swallow dquot recovery verification errors
Commit: e506e127fcb4e2bad1045805f1740b395eea9618
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e506e127fcb4e2bad1045805f1740b395eea9618
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80529
Analysis date: Wed, 26 Aug 2026 13:58:37 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Borderline Moderate / Manual review recommended
Manual review required: YES

Summary:
XFS dquot log recovery could ignore a failed quota verification and continue recovery as if the quota item were valid, allowing corrupt quota metadata to be written back to disk and potentially causing persistent filesystem integrity or availability impact.

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

The original Linux kernel CVE announcement for CVE-2026-80529 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80529

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.

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

CVE-2026-80529	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	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:H/A:H';CWE-703;CWE-252;CWE-754;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:L/A:L';BEST CVSS score: '5.7';DESCR 'XFS dquot log recovery could discard a verification failure because xlog_recover_dquot_commit_pass2 returned success from the cleanup path even after xfs_dqblk_verify reported corruption. This allows log recovery to continue as if the recovered quota record were valid, and the corrupt quota buffer may be written back to disk. For the CVSS the PR:H is used because reliable triggering normally requires administrative control over mounting or recovering an XFS filesystem image or block device. The issue is not network reachable and does not show a kernel memory corruption primitive. Impact is mainly persistent filesystem or quota metadata integrity loss and possible availability impact if the corrupted metadata later causes recovery or quota handling failures.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline Moderate / Manual review recommended (with actual score 3) 	MAYBE	DANGER DISK SIMPLEFIX  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=3
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 3
* Final recommended bucket: **Borderline Moderate / Manual review recommended**

## 2. Signal breakdown

* Important filesystem/storage path: +1
  XFS log recovery and quota metadata are persistent filesystem integrity paths.

* Integrity impact plausible: +1
  A corrupt recovered dquot can be accepted as valid and written back to disk.

* Availability impact realistic: +1
  Persistent quota metadata corruption may later cause recovery failures, quota malfunction, or filesystem-level disruption.

* Broad/default/common subsystem: +1
  XFS is a widely deployed production filesystem, although the vulnerable path is specific to dquot log recovery.

* Requires admin/root/CAP_SYS_ADMIN in typical deployments: -2
  Reliable triggering normally requires control over mounting or recovering a corrupted or crafted XFS filesystem image or block device.

* Paranoid privilege refinement: +1 relative to conservative
  In environments with delegated mount/storage handling, VM image ingestion, removable media, or automated recovery services, the attacker might influence the filesystem image without full host-root equivalence.

## 3. Reachability analysis

The bug is locally reachable through XFS log recovery of a filesystem containing a corrupt quota item. In typical deployments, mounting or recovering such a filesystem requires root or CAP_SYS_ADMIN, so this is not a normal unprivileged local trigger. It is not network reachable. Containers do not usually lower the requirement unless the container or service is allowed to provide block devices, filesystem images, or trigger host-side mounts. The path is relevant for XFS systems with quota metadata recovery, but exploitation requires a corrupted or attacker-influenced filesystem/log state.

Call-site confidence: high, because the provided commit describes the caller consequence directly: `xlog_recover_items_pass2()` sees success and recovery proceeds.

## 4. Severity interpretation

This behaves more like a filesystem integrity Moderate than a memory-corruption Important. The patch does not show UAF, OOB access, arbitrary write, type confusion, or a kernel memory lifetime primitive. The main practical impact is persistent acceptance and writeback of corrupted quota metadata. Manual review is still useful because filesystem recovery bugs can have durable integrity and availability impact, especially when untrusted filesystem images are mounted or processed automatically.

## 5. One-sentence report phrase

XFS dquot log recovery could ignore a failed quota verification and continue recovery as if the quota item were valid, allowing corrupt quota metadata to be written back to disk and potentially causing persistent filesystem integrity or availability impact.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: not Important-class based on the patch alone, but persistent XFS metadata integrity impact and possible delegated image-processing scenarios make it unsuitable for blind auto-close.

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

Patch: xfs: don't swallow dquot recovery verification errors
Commit: e506e127fcb4e2bad1045805f1740b395eea9618
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e506e127fcb4e2bad1045805f1740b395eea9618

Commit description:

xlog_recover_dquot_commit_pass2() validates the recovered dquot with
xfs_dqblk_verify() and, on failure, sets error = -EFSCORRUPTED and jumps
to out_release.  But out_release unconditionally returns 0, so the
corruption error is discarded: the caller xlog_recover_items_pass2()
sees success, log recovery proceeds as if the dquot were valid, and the
corrupt quota buffer can be written back to disk.

Fixes: 9c235df ("xfs: dquot recovery does not validate the recovered dquot")
Cc: stable@vger.kernel.org # v6.8
Signed-off-by: Long Li <leo.lilong@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  fs/xfs/xfs_dquot_item_recover.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=e506e127fcb4e2bad1045805f1740b395eea9618

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

The original Linux kernel CVE announcement for CVE-2026-80529 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80529

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:L/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:H/A:H
  The Best / paranoid CVSS score: 5.7

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: 2
  Paranoid ActionableScore: 3

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).