[CVE-2026-80531][MODERATE 7.0] xfs: avoid UAF on sc->tempip in xrep_tempfile_create

[CVE-2026-80531][MODERATE 7.0] xfs: avoid UAF on sc->tempip in xrep_tempfile_create

[AL-KERNEL]

CVE: CVE-2026-80531
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: xfs: avoid UAF on sc->tempip in xrep_tempfile_create
Commit: 08a20776ce33a2a52d856911e447c59424f0465a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=08a20776ce33a2a52d856911e447c59424f0465a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80531
Analysis date: Wed, 26 Aug 2026 12:47:19 -0400
ActionableScore: 6
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A potential use-after-free in XFS online repair can leave `sc->tempip` pointing to a released temporary inode after an error path, allowing later cleanup logic to dereference stale kernel memory and potentially crash the system.

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

The original Linux kernel CVE announcement for CVE-2026-80531 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80531

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-2026-80531	MODERATE	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	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-672;CWE-703;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A potential use-after-free exists in the XFS online repair temporary file creation path because sc tempip can keep referencing a temporary inode after xchk_irele releases it on an error path. If later cleanup or repair logic uses sc tempip again, the kernel may dereference a stale inode pointer and crash, with a worst case possibility of memory corruption depending on object lifetime and reuse. For the CVSS the PR:L is used in the paranoid score because a local user may be able to influence repair inputs or resource failure conditions while a privileged scrub or repair service runs, although direct online repair invocation normally requires CAP_SYS_ADMIN. The issue is not network reachable and requires local filesystem activity on an affected XFS setup. Impact is at least local denial of service via kernel crash and in worst case may allow confidentiality or integrity impact due to use-after-free memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5) 	MAYBE	DISK UAF LINUS  DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN6 DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP	-	-	checked

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

ActionableScore=6
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 6
* Final recommended bucket: **Actionable Moderate at minimum**::

This is not a Strong Important candidate on the supplied evidence, but it should not be auto-closed because the patch explicitly fixes a potential stale inode pointer / UAF in XFS online repair code.

## 2. Signal breakdown

Conservative score:

* +2 Generic memory corruption: the commit explicitly says potential UAF on `sc->tempip`.
* +1 Real lifetime corruption: `xchk_irele(sc, sc->tempip)` releases the inode, and without clearing `sc->tempip` later cleanup could observe a stale pointer.
* +1 Important filesystem/storage path: XFS online repair and inode handling are filesystem integrity paths.
* +1 Availability impact realistic: a later stale inode dereference can plausibly crash the kernel.
* -2 Requires admin/root/CAP_SYS_ADMIN in typical deployments: XFS online repair is normally invoked by privileged scrub/repair tooling.

Paranoid score:

* +1 Local unprivileged trigger/influence: if a privileged scrub/repair service processes attacker-controlled filesystem contents, a local user may influence the repair inputs or error path even without directly invoking repair.
* +1 Weak LPE concern: UAF on an inode object deserves manual review, but no reclaim, overwrite, callback control, or type confusion primitive is shown.
* -1 Special error path required: the bug requires tempfile creation to fail after `sc->tempip` has been set.

Paranoid total: 6.

## 3. Reachability analysis

The direct caller context is XFS online repair, which is usually administrator-controlled and not exposed to remote attackers. In typical deployments, triggering requires CAP_SYS_ADMIN or a privileged `xfs_scrub` / repair workflow, so the conservative score applies the admin penalty.

The paranoid case is still relevant because local users may be able to create or modify filesystem state that a privileged repair service later processes. Namespace or container environments do not automatically make this unprivileged, but reduced-privilege service or container-root models could lower practical PR from full host-root to local-user influence.

Call-site confidence: medium. The patch context shows the stale pointer assignment and release path, but not all later cleanup users of `sc->tempip`.

## 4. Severity interpretation

This behaves more like Actionable Moderate than ordinary Moderate because it is an explicit lifetime bug in a filesystem repair path. Realistic exploitation evidence is limited: there is no demonstrated reclaim primitive, attacker-controlled replacement, write-after-free, or type confusion. The most likely impact is local kernel crash during privileged repair. The theoretical worst case is stronger because stale inode pointers can sometimes become memory corruption primitives after object reuse, so manual review is justified.

## 5. One-sentence report phrase

A potential use-after-free in XFS online repair can leave `sc->tempip` pointing to a released temporary inode after an error path, allowing later cleanup logic to dereference stale kernel memory and potentially crash the system.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: explicit UAF candidate in XFS inode lifetime handling, with plausible local influence through filesystem repair workflows, but insufficient evidence for confirmed LPE without deeper call-site and object-reuse analysis.

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

Patch: xfs: avoid UAF on sc->tempip in xrep_tempfile_create
Commit: 08a20776ce33a2a52d856911e447c59424f0465a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=08a20776ce33a2a52d856911e447c59424f0465a

Commit description:

LOLLM noticed a potential UAF if the tempfile creation code fails after
it set sc->tempip.  Fix that.

Cc: stable@vger.kernel.org # v6.10
Fixes: 84c14ee ("xfs: create temporary files and directories for online repair")
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/tempfile.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=08a20776ce33a2a52d856911e447c59424f0465a

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

The original Linux kernel CVE announcement for CVE-2026-80531 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80531

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: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: 3
  Paranoid ActionableScore: 6

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).