[CVE-2026-97617][MODERATE REGULAR] ring-buffer: Check resize_disabled before publishing the new subbuf order

[CVE-2026-97617][MODERATE REGULAR] ring-buffer: Check resize_disabled before publishing the new subbuf order

[AL-KERNEL]

CVE: CVE-2026-97617
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: ring-buffer: Check resize_disabled before publishing the new subbuf order
Commit: f2099644e1b2a2c0805c5240d63ab0522d9d0174
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f2099644e1b2a2c0805c5240d63ab0522d9d0174
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97617
Analysis date: Fri, 25 Sep 2026 12:26:45 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline / manual review recommended
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-97617 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97617

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.

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

CVE-2026-97617	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-97617 CHECK WITH IMPACT FROM ORIG NN LOW	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:N/A:H';CWE-362;CWE-125;*CWE-200;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:L';BEST CVSS score: '6.3';DESCR 'A race exists between ring_buffer_subbuf_order_set and the lockless mmap path. The order setter can publish a new subbuf_order before discovering that resizing is disabled and returning EBUSY. A concurrent __rb_map_vma operation can read the temporary order, calculate a larger mapping, and insert pages beyond the intended sub-buffer boundary into the user VMA. This provides a plausible out-of-bounds mapping and information disclosure primitive, while a malformed mapping may also cause a fault or availability impact. For the CVSS the PR:L value is used for the paranoid score because tracefs access can be delegated to a restricted service account, container root, or another user with limited tracing permissions. AC:H applies because successful triggering requires winning a race between mmap and the failing order change. The issue is locally triggered and is not network reachable. Impact is at least unintended page exposure and in the worst defensible case may include substantial confidentiality and availability impact. No writable mapping or concrete arbitrary write primitive is established, so integrity impact remains I:N.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4)  SKIP CVE-2026-97617 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	READ TRACE SIMPLEFIX HARDWARE LINUS  INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP	-	-	checked

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

ActionableScore=4
ActionableScoreLower=3
PrimitiveClass=CLASS_B
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 3
* Conservative score: 3
* Raw paranoid score: 4
* Paranoid score: 4
* No floor or cap was applied.
* Final recommended bucket: **Borderline / manual review recommended**::

2. Signal breakdown

Conservative signals:

* +1 Weak or indirect corruption candidate. The race creates inconsistent sub-buffer geometry and causes pages beyond the intended sub-buffer boundary to be inserted into a userspace VMA.
* +1 Active-state synchronization bypass. An existing user mapping sets resize_disabled, but the vulnerable path publishes the replacement order before checking that guard. The fix restores the check before publication.
* +1 Confidentiality plausible. The extra pages are mapped into a user-visible VMA, providing a concrete disclosure path rather than merely an internal kernel OOB read.

Paranoid-only signal:

* +1 Reliable kernel fault or strong DoS concern. The inconsistent order can make the mmap path walk or insert pages beyond the intended sub-buffer geometry. A host fault is technically defensible, although the commit does not document an observed panic.

Not awarded:

* No UAF or post-lifetime stale-object use is established.
* No controlled reclaim, arbitrary write, writable unintended mapping, or attacker-directed target is demonstrated.
* No integrity point was awarded because the evidence establishes page insertion into a VMA but not unauthorized modification through that mapping.
* No remote-reachability point was awarded.
* No local-unprivileged point was awarded because access to both mmap and sub-buffer order control below host-admin privilege is not established.
* No race penalty was applied. The input does not establish that repeated attempts are impractical or that the timing window is one-shot.
* No extra Availability point was awarded for the same possible fault.
* No repeated release or refcount operation exists. The repeated-release signal and UAF floors do not apply.
* The memory-layout invariant was not scored separately because it is the same underlying fact as the inconsistent out-of-range mapping.

3. Reachability analysis

The complete trigger requires one path to attempt changing subbuf_order while another performs mmap against an already mapped CPU whose resize_disabled counter is set. The attacker therefore needs access to both the ring-buffer mapping interface and the order-changing control path, or cooperation with another actor performing the resize.

The supplied evidence does not prove whether those operations require host-admin-equivalent tracing privileges or are available to a delegated tracing user. Therefore HostAdminRequired is UNKNOWN rather than YES or NO. No evidence establishes that the complete operation is governed by attacker-obtainable user-namespace or tracing-namespace privileges, so NamespaceScopedPrivilege is also UNKNOWN.

The issue is local and not directly network-triggerable. No special hardware is required. A configured trace ring buffer and permission to access its mmap and resize interfaces are prerequisites. Although triggering requires a race, the evidence does not show that the race is intrinsically narrow or non-repeatable.

4. Primitive and severity interpretation

The exact primitive is a transient mismatch between published sub-buffer order and the actual non-resized buffer layout. The lockless mmap path consumes the transient order and inserts pages beyond the intended sub-buffer boundary into a user VMA.

This is an active mapping and synchronization violation, not a UAF, double release, or controlled overwrite. Its strongest patch-supported non-crash consequence is unintended user-visible page exposure. The extent and sensitivity of those pages are unresolved. A kernel fault is a defensible paranoid consequence, but it is not explicitly demonstrated.

PrimitiveClass is CLASS_B because the patch establishes an independently useful out-of-range mapping and possible disclosure primitive, but not a strong controlled corruption primitive. ImportantCandidate is NO because substantial kernel disclosure, arbitrary access, integrity modification, LPE, and security-boundary bypass are not established. AutoDowngradeAllowed is YES because the unresolved behavior remains limited to constrained unintended mapping and possible DoS, without Class A leverage. Manual review is still recommended to determine exactly which pages become visible and whether the VMA is strictly read-only.

5. One-sentence report phrase

A race between sub-buffer order publication and the lockless ring-buffer mmap path can map pages beyond the intended sub-buffer boundary into userspace, creating a local information-disclosure risk and a possible kernel fault.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Verify the maximum mapping overrun, the ownership and contents of the extra pages, VMA write permissions, and the actual privilege checks for mmap and sub-buffer resizing.

7. Call-site confidence

Call-site confidence: medium

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

Patch: ring-buffer: Check resize_disabled before publishing the new subbuf order
Commit: f2099644e1b2a2c0805c5240d63ab0522d9d0174
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f2099644e1b2a2c0805c5240d63ab0522d9d0174

Commit description:

ring_buffer_subbuf_order_set() stores the new order and only then walks
the CPUs, returning -EBUSY if any of them has resizing disabled. A user
mapped buffer has resizing disabled, and __rb_map_vma() reads
buffer->subbuf_order without buffer->mutex, so an mmap of an already
mapped CPU racing the failing order change sizes the mapping with the
new order and inserts pages past the sub-buffer into the VMA.

Check the CPUs before storing the new order.

Cc: stable@vger.kernel.org
Fixes: 117c392 ("ring-buffer: Introducing ring-buffer mapping functions")
Link: https://patch.msgid.link/20260912103938.1127021-1-devnexen@gmail.com
Signed-off-by: David Carlier <devnexen@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  kernel/trace/ring_buffer.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=f2099644e1b2a2c0805c5240d63ab0522d9d0174

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

The original Linux kernel CVE announcement for CVE-2026-97617 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97617

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:H/I:N/A:H
  The Best / paranoid CVSS score: 6.3

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: 3
  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: 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).