[CVE-2026-80528][MODERATE 7.0] ceph: avoid fs reclaim while using current->journal_info [ Upstream

[CVE-2026-80528][MODERATE 7.0] ceph: avoid fs reclaim while using current->journal_info [ Upstream

[AL-KERNEL]

CVE: CVE-2026-80528
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: ceph: avoid fs reclaim while using current->journal_info [ Upstream
Commit: ca5fa2380dd90a0adb01580fa6225025351a90f6
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ca5fa2380dd90a0adb01580fa6225025351a90f6
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80528
Analysis date: Wed, 26 Aug 2026 11:14:24 -0400
ActionableScore: 6
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: NO

Summary:
Ceph MDS reply handling can enter filesystem reclaim while `current->journal_info` contains Ceph private data, allowing ext4/JBD2 to misinterpret it as a journal handle and crash the kernel under memory reclaim conditions.

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

The original Linux kernel CVE announcement for CVE-2026-80528 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80528

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: NO

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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

CVE-2026-80528	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';CWE-843;CWE-704;CWE-703;Other CVSS 'AV:A/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.9';DESCR 'Ceph MDS reply handling temporarily stores a Ceph request pointer in current journal_info while filling inode and dentry cache. An allocation in this section can enter direct reclaim and run shrinkers from another filesystem. If ext4 dirties an inode during that reclaim path, JBD2 may interpret the Ceph request as a journal handle and dereference request fields as JBD2 state, leading to an invalid pointer dereference and kernel crash. For the CVSS the PR:L is used because reliable triggering normally requires a local process or service workload that accesses the mounted Ceph filesystem and causes MDS replies to be processed. The issue is network adjacent in typical Ceph deployments because a malicious or compromised MDS path can influence replies, but practical exploitation depends on an already mounted Ceph filesystem and memory reclaim timing. Impact is at least denial of service via kernel crash. In the paranoid interpretation, limited confidentiality or integrity impact is kept for manual review because the bug is a cross filesystem type confusion around current journal_info, but no direct arbitrary write primitive is established.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	OOB DEADLOCK DANGER DISK KERNEL_PANIC_PLUS_UAF HARDWARE DEBUGFS KPANIC 	NO	NO	checked

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

ActionableScore=6
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 6
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* +1 Local unprivileged trigger: a local user or workload that can access an already mounted Ceph filesystem can cause MDS reply handling and cache population paths to run.
* +1 Network-adjacent MDS-mediated influence: the affected data path processes Ceph MDS replies, but this is not a generic Internet-facing remote vector and normally requires a mounted Ceph filesystem and access to the Ceph cluster path.
* +1 Memory corruption, weak/indirect corruption candidate: JBD2 interprets `current->journal_info` as a journal handle while it actually contains a `ceph_mds_request`, which is a cross-subsystem type confusion / invalid struct interpretation.
* +1 Reliable kernel crash / strong DoS: the commit provides a concrete Oops in `jbd2__journal_start()`.
* +1 Important filesystem/storage path: the bug crosses Ceph MDS reply processing, VFS reclaim, dcache pruning, ext4 inode dirtying, and JBD2 journaling.
* -1 Hard or unreliable timing / special conditions: triggering requires allocation during Ceph reply handling, direct reclaim, shrinkers hitting another filesystem, and ext4/JBD2 interpreting the same task-local `journal_info`.

Paranoid additional signals:

* +1 Confidentiality impact plausible: limited C impact is kept only for manual-review sensitivity because this is type confusion in a privileged filesystem/journal path.
* +1 Integrity impact plausible: limited I impact is defensible for triage because JBD2 consumes a mis-typed pointer as transaction state, but no arbitrary write primitive is demonstrated.

Not awarded:

* No +2 remote reachable: exposure is Ceph-cluster / MDS-path dependent, not a generally reachable network protocol surface.
* No +2 strong LPE plausibility: no attacker-controlled reclaim replacement, arbitrary write, callback control, or demonstrated privilege escalation primitive.
* No +2 strong memory corruption: the demonstrated primitive is invalid struct interpretation ending in crash, not proven controllable corruption.

## 3. Reachability analysis

A realistic trigger requires a system with a mounted Ceph filesystem and MDS replies being processed by the kernel client. A local user may be able to trigger directory operations such as readdir on the mounted Ceph filesystem, but reliable reproduction also depends on memory pressure and direct reclaim entering another filesystem path such as ext4. A malicious or compromised Ceph MDS, or a trusted internal Ceph network path under attacker influence, can affect the timing and content of MDS replies, but this should be treated as network-adjacent rather than broadly remote Internet reachability.

Namespaces and containers may matter if a container or reduced-privilege workload has access to a host-mounted Ceph filesystem and can generate filesystem activity. The initial mount setup is privileged, but triggering after deployment may not require full host root.

Call-site confidence: high. The provided trace and patch show the relevant path from `ceph_readdir_prepopulate()` through reclaim into ext4/JBD2.

## 4. Severity interpretation

This behaves above an ordinary Moderate because it is a real kernel crash in an important filesystem path with cross-filesystem type confusion. Conservative handling is borderline manual-review territory, not auto-close. The paranoid interpretation reaches Actionable Moderate because limited C/I concern is defensible for triage, but the patch does not show a controlled write, UAF reclaim, refcount takeover, or direct LPE primitive. Realistic impact is strongest for DoS, while privilege escalation remains speculative.

## 5. One-sentence report phrase

Ceph MDS reply handling can enter filesystem reclaim while `current->journal_info` contains Ceph private data, allowing ext4/JBD2 to misinterpret it as a journal handle and crash the kernel under memory reclaim conditions.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: the demonstrated impact is a kernel crash, but the bug crosses network filesystem input, reclaim, ext4/JBD2 journaling, and task-local type confusion, so it should not be auto-closed without human review.

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

Patch: ceph: avoid fs reclaim while using current->journal_info [ Upstream
Commit: ca5fa2380dd90a0adb01580fa6225025351a90f6
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ca5fa2380dd90a0adb01580fa6225025351a90f6

Changed files:
  fs/ceph/mds_client.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=ca5fa2380dd90a0adb01580fa6225025351a90f6

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

The original Linux kernel CVE announcement for CVE-2026-80528 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80528

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:A/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:A/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 5.9

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: 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: 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).