[CVE-2026-89618][LOW] eventfs: Initialize ei->children and ei->list in init_ei()

[CVE-2026-89618][LOW] eventfs: Initialize ei->children and ei->list in init_ei()

[AL-KERNEL]

CVE: CVE-2026-89618
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: eventfs: Initialize ei->children and ei->list in init_ei()
Commit: c480f8af173d5b19c6d9c4311df6bbe352face9e
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c480f8af173d5b19c6d9c4311df6bbe352face9e
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89618
Analysis date: Sat, 12 Sep 2026 01:45:27 -0400
ActionableScore: 1
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-89618 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89618

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.

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

CVE-2026-89618	LOW	https://www.kernelcve.org/list/?q=CVE-2026-89618 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:N/I:N/A:H';*CWE-457;CWE-665;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 'eventfs can issue a false WARN during an allocation failure path because eventfs_inode children and list list_head fields may be checked by free_ei before they are initialized. The practical trigger requires local conditions such as memory pressure during eventfs or tracefs directory creation. For the CVSS the PR:L is used for the paranoid score as a sensitivity case where a low privileged local process can influence memory pressure while privileged tracing activity triggers the failure path. The issue is not network reachable. Impact is normally limited to a warning, but systems configured with panic_on_warn may convert the warning into a kernel crash and local denial of service.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)  SKIP CVE-2026-89618 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	DISK INIT WARNONLY TRACE SIMPLEFIX IMPROVEONLY LINUS SYZBOT 	-	-	checked

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

ActionableScore=1
ActionableScoreLower=0
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 0
* Conservative score: 0
* Raw paranoid score: 1
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate**::

No floor or cap changed the score.

2. Signal breakdown

Conservative positive signals:

* +0. False WARN only. The patch establishes that uninitialized eventfs_inode list_head fields may be checked before initialization and produce a false warning.
* +0. No real UAF. No object is shown to be used after free.
* +0. No concrete memory corruption primitive. The described failure is an uninitialized list_head check in cleanup, not an OOB write, double free, controlled reclaim, arbitrary write, or refcount mutation.

Paranoid positive signals:

* +1. Conditional local DoS. On systems configured with panic_on_warn, the false WARN may become a kernel panic.

Negative signals:

* No negative privilege penalty was applied because host-admin-equivalent privilege for the complete trigger is not positively established.
* No race penalty was applied. The issue is an allocation-failure cleanup ordering bug, not a demonstrated hard race.

Non-awarded material signals:

* Controlled reclaim not demonstrated.
* Arbitrary write not demonstrated.
* Real UAF not demonstrated.
* Concrete repeated release/refcount operation not demonstrated.
* Structured stale-object leverage not awarded because the stale/lifetime primitive is absent.
* Confidentiality and integrity impact not awarded.
* Extra availability not awarded beyond the paranoid panic_on_warn case.
* Remote reachability not established.
* Authorization or security-boundary bypass not established.

3. Reachability analysis

The visible trigger requires eventfs or tracefs directory creation to fail after init_ei but before the old later list initialization points. The commit attributes the condition to memory pressure during eventfs_create_dir cleanup.

A local user may be able to contribute to memory pressure, but the supplied evidence does not prove that an ordinary unprivileged user can complete the full eventfs or tracefs directory creation path. The complete privilege boundary is therefore unresolved, so HostAdminRequired is UNKNOWN rather than YES or NO.

No namespace-scoped capability path is shown. No network trigger is present. No special hardware is required. The issue depends on an allocation failure path, not on attacker-controlled packet traffic or a broad unprivileged syscall data path.

4. Primitive and severity interpretation

The exact primitive is an uninitialized list_head state observed by cleanup code before list initialization. The demonstrated consequence is a false WARN.

This is not an active structured-object UAF and not fixed stale storage UAF. No first lifetime-ending operation followed by a second lifetime/refcount mutation is shown. No object reuse, callback use, arbitrary read/write, information disclosure, or privilege escalation path is established.

PrimitiveClass is CLASS_C because the behavior is warning/DoS style invalid-state behavior without an independently useful corruption primitive. ImportantCandidate is NO because there is no meaningful Important-vs-Moderate exploitation leverage. AutoDowngradeAllowed is YES because the established impact is warning-only in normal operation and at most panic_on_warn DoS in the paranoid case.

5. One-sentence report phrase

eventfs may issue a false WARN during an allocation failure cleanup path because eventfs_inode children and list list_head fields are checked before initialization, with practical impact normally limited to warning noise and only conditional DoS on panic_on_warn systems.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: no real UAF, no repeated release/refcount mutation, no memory corruption primitive, no security-boundary bypass, and no network or unprivileged complete trigger is established.

7. Call-site confidence

Call-site confidence: medium

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

Patch: eventfs: Initialize ei->children and ei->list in init_ei()
Commit: c480f8af173d5b19c6d9c4311df6bbe352face9e
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c480f8af173d5b19c6d9c4311df6bbe352face9e

Commit description:

eventfs_create_dir() allocates the eventfs_inode and initializes it with
init_ei(). But this does not initialize the eventfs_inode list_heads. If
the eventfs_create_dir() fails due to memory pressure, it will call
free_ei() before it initialized the lists, and that checks to make sure
the eventfs_inode has no children. But because the list wasn't
initialized, it will give a false warning.

Fix it by moving the list initialization into init_ei().

Cc: stable@vger.kernel.org
Fixes: 5790b1f ("eventfs: Remove eventfs_file and just use eventfs_inode")
Reported-by: syzbot+3ef80b4ed02226d04a06@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=3ef80b4ed02226d04a06
Link: https://patch.msgid.link/20260824144653.54044-1-kartikey406@gmail.com
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
[ Rewrote change log ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  fs/tracefs/event_inode.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=c480f8af173d5b19c6d9c4311df6bbe352face9e

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

The original Linux kernel CVE announcement for CVE-2026-89618 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89618

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: 1

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).