[CVE-2026-80535][LOW] xfs: don't double-lock when deleting a self-referential directory

[CVE-2026-80535][LOW] xfs: don't double-lock when deleting a self-referential directory

[AL-KERNEL]

CVE: CVE-2026-80535
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: xfs: don't double-lock when deleting a self-referential directory
Commit: 17bc347cbdfb125eddac0a815b1f6c1f6eb56676
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=17bc347cbdfb125eddac0a815b1f6c1f6eb56676
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80535
Analysis date: Wed, 26 Aug 2026 13:53:58 -0400
ActionableScore: 2
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A self-referential XFS directory can cause the online directory tree repair path to lock the same inode twice, leading to a local repair-path hang or DoS, typically requiring administrator-level filesystem repair access.

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

The original Linux kernel CVE announcement for CVE-2026-80535 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80535

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
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CVE-2026-80535	LOW	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:L/UI:N/S:U/C:N/I:N/A:H';CWE-667;*CWE-833;CWE-703;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'A self-referential XFS directory can make the directory tree repair path treat the same inode as both the scrub target and the parent directory. The old logic could try to lock the same inode twice during unlink repair, which can lead to a deadlock or hang in the repair path. For the CVSS the PR:L paranoid interpretation applies only if an untrusted local actor can reach the repair path through delegated filesystem administration or a privileged repair service that processes attacker controlled XFS metadata. In normal deployments PR:H is more realistic because XFS online repair and mounting attacker controlled filesystems require administrative privileges. The issue is not network reachable. Impact is denial of service only via repair hang or filesystem operation stall. For the paranoid score, this uses the highest still defensible DoS interpretation and does not change the bug class.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) 	MAYBE	DANGER DISK LINUS  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	-	-	checked

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

ActionableScore=2
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**::

## 2. Signal breakdown

Conservative signals:

* Reliable kernel crash / strong DoS: +1. The bug can deadlock or hang the XFS directory tree repair path by trying to lock the same inode twice.
* Important filesystem/storage path: +1. The affected code is XFS online scrub repair for directory metadata.
* Requires admin/root/CAP_SYS_ADMIN in typical deployments: -2. Running XFS online repair and handling corrupted filesystem metadata normally requires administrator-level filesystem management.
* Rare AND difficult-to-reach subsystem/configuration: -1. Triggering requires a self-referential corrupted directory and execution of the specific dirtree repair path.

Conservative total is clamped to 0.

Paranoid signals:

* Local unprivileged trigger: +1. Only under a delegated or service-mediated model where an untrusted local actor can provide attacker-controlled XFS metadata to a privileged repair workflow.
* Reliable kernel crash / strong DoS: +1. A repair-path hang or deadlock is plausible.
* Important filesystem/storage path: +1. XFS metadata repair is security-relevant storage code.
* Hard or special condition required: -1. The condition requires unusual filesystem corruption and a repair invocation.

Paranoid total: 2.

No memory corruption signal is awarded. The patch shows a double-locking logic bug, not UAF, OOB write, double free, stale pointer reuse, refcount misuse, page-cache corruption, or object confusion.

## 3. Reachability analysis

Typical reachability is local and privileged. The affected path is XFS online scrub repair, not normal file I/O and not network reachable. A normal unprivileged user generally cannot invoke this repair path against arbitrary corrupted metadata.

Namespaces and containers do not materially lower the conservative privilege requirement unless a container or service is explicitly delegated filesystem repair capabilities over attacker-controlled images or mounts. In such a special deployment, the paranoid PR:L-style interpretation is possible, but it is not the common case.

Call-site confidence: high. The patch directly shows the affected lock and unlock paths in `xrep_dirtree_unlink()` and `xrep_dirtree_unlink_iolock()`.

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like availability issue, not an Important-class vulnerability. The realistic impact is a repair-path deadlock or filesystem operation stall. There is no supported privilege escalation primitive and no confidentiality or integrity impact beyond the already corrupted filesystem metadata context.

The theoretical risk remains DoS-only. The patch does not support upgrading this to memory corruption or LPE.

## 5. One-sentence report phrase

A self-referential XFS directory can cause the online directory tree repair path to lock the same inode twice, leading to a local repair-path hang or DoS, typically requiring administrator-level filesystem repair access.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED.

Reason: no memory corruption, no remote reachability, no privilege escalation path, and no practical unprivileged trigger in normal deployments.

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

Patch: xfs: don't double-lock when deleting a self-referential directory
Commit: 17bc347cbdfb125eddac0a815b1f6c1f6eb56676
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=17bc347cbdfb125eddac0a815b1f6c1f6eb56676

Commit description:

LOLLM notices that the dirtree scrubber can detect a directory that
refers to itself.  In this case, it's not correct for the directory tree
repair code to try to iolock/ilock both sc->ip and dp, because they're
the same inode.  Fix this by detecting that corner case and handling it
appropriately.

Cc: stable@vger.kernel.org # v6.10
Fixes: 3f31406 ("xfs: fix corruptions in the directory tree")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Assisted-by: LOLLM # finding obvious bugs
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  fs/xfs/scrub/dirtree_repair.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=17bc347cbdfb125eddac0a815b1f6c1f6eb56676

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

The original Linux kernel CVE announcement for CVE-2026-80535 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80535

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:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: 0
  Paranoid ActionableScore: 2

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).