[CVE-2026-99204][MODERATE 7.0] ocfs2/dlm: Protect the recovery list during debugfs reads [ Upstream commit 4c435828932bf46f29860e4a0375bcae101b778a ]

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-99204
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: ocfs2/dlm: Protect the recovery list during debugfs reads [ Upstream commit 4c435828932bf46f29860e4a0375bcae101b778a ]
Commit: 04d4571c00db61a9664f387752fa05cb3c08a537
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=04d4571c00db61a9664f387752fa05cb3c08a537
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99204
Analysis date: Wed, 28 Oct 2026 23:17:16 -0400
ActionableScore: 4
ActionableScore lower bound: unknown
Actionable bucket: Borderline / manual review recommended
Manual review required: YES

Summary:
A concurrent OCFS2 DLM debugfs read can traverse freed recovery records, causing a limited stale-data disclosure or kernel fault.

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

The original Linux kernel CVE announcement for CVE-2026-99204 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99204

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-2026-99204	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-99204 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=2 LEGACY=MODERATE_KPANIC RESULT=SAME V39_AEGIS_ONE_STEP_UP=MODERATE->MODERATE_KPANIC (final reconciliation agrees; DECISION: both MODERATE_KPANIC)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:H';*CWE-416;CWE-362;CWE-667;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:L';BEST CVSS score: '5.3';DESCR 'A race in OCFS2 DLM debug_state_print allows a debugfs reader to traverse recovery participant records after dlm_destroy_recovery_area has detached and freed them. KASAN confirms a slab use after free read of record fields. The demonstrated primitive is an invalid read that may disclose limited reused slab data or cause a kernel fault, with no supported write primitive or privilege escalation path. For the CVSS the PR:L paranoid value covers deployments that delegate access to this diagnostic file, while normal debugfs access commonly requires administrative privileges. AC:H applies because exploitation requires overlap with recovery record destruction. Automated impact decision path. The original SimpleNet classifier selected MODERATE. The primary LLM estimated paranoid CVSS 5.3 and the production ActionableScore returned 4 with recommendation Borderline / manual review recommended. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were final reconciliation stage MODERATE to MODERATE_KPANIC because the cross model evidence reconciliation rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 2.5 and ActionableScore 2 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4)	MAYBE	READ OOB LOCK DISK PRINTF-TTY LEAK UAF HARDWARE DEBUGFS LINUS  KPANIC V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED	-	-	checked

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

ActionableScore=4
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 4.
* Conservative score: 4; the real-UAF floor of 4 is satisfied without adjustment.
* Raw paranoid score: 4.
* Paranoid score: 4; no additional exploit primitive is technically supported.
* Final recommended bucket: **Borderline / manual review recommended**::

2. Signal breakdown

* +2 — Confirmed slab UAF: recovery records are freed by `dlm_destroy_recovery_area()` while `debug_state_print()` can still traverse and read them.
* +1 — Plausible kernel fault/DoS from dereferencing freed list entries or fields.
* +1 — Limited disclosure path: freed `state` and `node_num` values are formatted into the debugfs output returned to the reader.
* +0 — No race penalty: concurrency is required, but the stress task reproduced it; evidence does not establish a narrow, one-shot, uncontrollable race.
* +0 — No privilege penalty because the debugfs file permissions and delegation model are not supplied.
* No write, controlled reclaim, callback use, repeated release, arbitrary access, or integrity impact is shown. The same possible crash is not counted again as Availability.

3. Reachability analysis

A process able to open the OCFS2 DLM debugfs state file can race recovery-area destruction. The report used UID 0, but this does not prove host-admin privilege is inherently required, nor does it establish delegated low-privilege access. The complete privilege and namespace boundary therefore remain unknown. OCFS2 DLM recovery and mounted debugfs are prerequisites; no special hardware is required.

4. Primitive and severity reading

This is an active structured-object UAF, but the stale use is a shallow diagnostic traversal that reads integer fields for formatting. The fix applies the recovery-list lock across traversal, directly proving the lifetime race. Shown effects are a KASAN-detected read, plausible fault, and limited stale-data output. There is no post-free write or material reuse primitive, so this remains constrained CLASS_B rather than an Important-keeping UAF. B5-R, B3-PENDING, and B4-PENDING do not apply.

5. One-sentence report phrase

A concurrent OCFS2 DLM debugfs read can traverse freed recovery records, causing a limited stale-data disclosure or kernel fault.

6. Manual review advice

MANUAL CHECK RECOMMENDED

Confirm debugfs permissions and whether non-admin users can access the affected file in supported deployments.

7. Call-site confidence

Call-site confidence: high

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

Patch: ocfs2/dlm: Protect the recovery list during debugfs reads [ Upstream commit 4c435828932bf46f29860e4a0375bcae101b778a ]
Commit: 04d4571c00db61a9664f387752fa05cb3c08a537
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=04d4571c00db61a9664f387752fa05cb3c08a537

Commit description:

Recovery participant records must remain alive while debug_state_print()
walks reco.node_data and formats their fields. The formatter holds
dlm->spinlock, but the recovery participant list is protected by
dlm_reco_state_lock. In particular, dlm_destroy_recovery_area() detaches
the list under dlm_reco_state_lock and frees the detached records after
releasing it. A concurrent debugfs open can therefore read freed memory.

Protect the participant traversal and field reads in debug_state_print()
with dlm_reco_state_lock, matching the existing list writers. This also
serializes the traversal against list_add_tail() during recovery-area
initialization. Make the existing lock available to the debug code
through dlmcommon.h; the lock remains internal to the OCFS2 DLM module.

Release dlm->spinlock after formatting the other domain state and before
acquiring dlm_reco_state_lock, so the debug reader does not nest the two
locks. Leave recovery list insertion, detachment and freeing unchanged.

KASAN report as below:

    BUG: KASAN: slab-use-after-free in debug_state_open+0x1169/0x12d0
    Read of size 4 at addr ffff88810662ef80 by task dlm-state-stres/896

    CPU: 1 UID: 0 PID: 896 Comm: dlm-state-stres Not tainted 7.3.0-rc4-next-20260921-pmb-ocfs2-functional-v1+ #1 PREEMPT(lazy)
    Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
    Call Trace:
     <TASK>
     dump_stack_lvl+0x93/0xd0
     print_report+0xce/0x630
     ? debug_state_open+0x1169/0x12d0
     ? srso_alias_return_thunk+0x5/0xfbef5
     ? __virt_addr_valid+0x20e/0x420
     ? debug_state_open+0x1169/0x12d0
     kasan_report+0xe0/0x110
     ? debug_state_open+0x1169/0x12d0
     debug_state_open+0x1169/0x12d0
     ? __pfx_debug_state_open+0x10/0x10
     full_proxy_open_regular+0x193/0x310
     do_dentry_open+0x595/0x12d0
     ? __pfx_full_proxy_open_regular+0x10/0x10
     vfs_open_consume+0xd1/0x400
     ? srso_alias_return_thunk+0x5/0xfbef5
     path_openat+0x18d0/0x2020
     ? __pfx_path_openat+0x10/0x10
     do_file_open+0x21e/0x470
     ? __pfx_do_file_open+0x10/0x10
     ? _raw_spin_unlock+0x23/0x40
     ? srso_alias_return_thunk+0x5/0xfbef5
     ? alloc_fd+0x3a6/0x6b0
     do_sys_openat2+0xf4/0x1b0
     ? __pfx_do_sys_openat2+0x10/0x10
     ? srso_alias_return_thunk+0x5/0xfbef5
     ? __fput+0x5b5/0xa60
     __x64_sys_openat+0x136/0x1e0
     ? __pfx___x64_sys_openat+0x10/0x10
     do_syscall_64+0x114/0x620
     entry_SYSCALL_64_after_hwframe+0x77/0x7f
    [Register dump omitted.]
     </TASK>

    Allocated by task 880:
     kasan_save_stack+0x33/0x60
     kasan_save_track+0x14/0x30
     __kasan_kmalloc+0xaa/0xb0
     __kmalloc_cache_noprof+0x28d/0x610
     dlm_remaster_locks+0x147/0x1d90
     dlm_do_recovery+0xde1/0x1580
     dlm_recovery_thread+0x109/0x300
     kthread+0x351/0x460
     ret_from_fork+0x659/0x940
     ret_from_fork_asm+0x1a/0x30

    Freed by task 880:
     kasan_save_stack+0x33/0x60
     kasan_save_track+0x14/0x30
     kasan_save_free_info+0x3b/0x60
     __kasan_slab_free+0x5f/0x80
     kfree+0x308/0x580
     dlm_destroy_recovery_area+0x285/0x460
     dlm_remaster_locks+0x17c4/0x1d90
     dlm_do_recovery+0xde1/0x1580

[Commit description truncated; see the upstream URL below]

Changed files:
  fs/ocfs2/dlm/dlmdebug.c
  fs/ocfs2/dlm/dlmrecovery.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=04d4571c00db61a9664f387752fa05cb3c08a537

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

The original Linux kernel CVE announcement for CVE-2026-99204 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99204

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:L/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:H
  The Best / paranoid CVSS score: 5.3

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: 4

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).