[CVE-2026-89601][LOW] ext2: Fix lost inode updates for IS_SYNC inodes

[CVE-2026-89601][LOW] ext2: Fix lost inode updates for IS_SYNC inodes

[AL-KERNEL]

CVE: CVE-2026-89601
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: ext2: Fix lost inode updates for IS_SYNC inodes
Commit: 5efb3350230fef831167740e69e6db2861101186
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5efb3350230fef831167740e69e6db2861101186
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89601
Analysis date: Fri, 11 Sep 2026 23:51:18 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
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-2026-89601 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89601

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-2026-89601	LOW	https://www.kernelcve.org/list/?q=CVE-2026-89601 CHECK WITH IMPACT FROM ORIG NN MODERATE	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:L/A:L';CWE-754;CWE-703;*CWE-664;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N';BEST CVSS score: '3.6';DESCR 'ext2 IS_SYNC inode updates could be lost because metadata sync was requested before the inode was marked dirty. This can cause file size timestamp or xattr block pointer changes to remain only in memory and not be persisted to disk, with practical impact after a crash power loss or similar interruption. For the CVSS the PR:L value is used because a local user or process with permission to modify files or xattrs on an affected ext2 filesystem can reach the vulnerable paths. The issue is not network reachable and does not indicate memory corruption or privilege escalation. Impact is mainly low integrity loss for filesystem metadata, with possible low availability impact in the paranoid case if affected files become inconsistent or unusable.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)  SKIP CVE-2026-89601 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	DISK SIMPLEFIX LINUS  DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS	-	-	checked

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

ActionableScore=2
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 2
* Conservative score: 2
* Raw paranoid score: 2
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate**::

No floor or cap was applied.

2. Signal breakdown

Positive signals:

* +1 Local unprivileged trigger. A local user or process with normal permission to modify files or xattrs on an already mounted affected ext2 filesystem can reach ext2_setsize() or ext2_xattr_set2().
* +1 Filesystem metadata persistence or integrity issue. The bug can lose inode metadata updates for IS_SYNC inodes because sync_inode_metadata() was called before mark_inode_dirty(), so size, timestamps, or xattr block pointer updates may not be persisted.

Negative or non-awarded signals:

* +0 Real UAF not awarded. No stale pointer, post-free object use, double release, or refcount lifetime corruption is established.
* +0 Memory corruption not awarded. The patch fixes ordering of dirty marking and metadata sync, not an OOB, UAF, write primitive, or type confusion.
* +0 Reliable kernel crash not awarded. The demonstrated consequence is lost persistence of metadata updates, not panic or host-wide crash.
* +0 Confidentiality not awarded. There is no disclosure path.
* +0 Strong integrity or COW ownership bypass not awarded. The issue affects persistence of authorized updates, not an attacker-authorized write to a different protected object.
* +0 Availability not awarded separately. Affected files may become inconsistent after crash or power loss, but this is not a distinct host-wide availability primitive for ActionableScore.
* +0 Remote reachability not established. This is a local filesystem operation path.
* +0 Important filesystem path not separately awarded. ext2 inode/xattr metadata is security-relevant enough for the metadata signal, but the issue is limited and does not involve journal recovery, shared page ownership, page cache corruption, or extent/refcount ownership violation.
* No concrete negative privilege penalty. Host-admin privilege is not required when the affected ext2 filesystem and relevant files already exist.

3. Reachability analysis

The realistic trigger is local. A user who can modify a file, truncate a file, or set permitted xattrs on an affected ext2 filesystem can reach the relevant code paths. The condition is limited to IS_SYNC inodes or equivalent sync behavior, and the practical harmful effect normally requires an interruption such as crash or power loss before metadata is otherwise persisted.

Host administrator privilege may be required to create or mount the ext2 filesystem, or to configure some system-wide mount options. That is prior deployment context, not necessarily a privilege required for every trigger once the filesystem is available. No namespace-scoped capability chain is involved. No network path, special hardware, race window, or memory lifetime manipulation is established.

4. Primitive and severity interpretation

The exact primitive is a metadata persistence ordering bug. The inode is updated, but for IS_SYNC cases the code attempted sync_inode_metadata() before marking the inode dirty. Since sync_inode_metadata() only acts on already dirty inodes, the intended metadata update could be lost.

This is not active structured UAF, fixed stale storage, double release, refcount mutation, or cleanup-only stale dereference. There is no first lifetime operation that may free an object and no second lifetime mutation through a dangling reference.

PrimitiveClass=NONE because no kernel corruption, ownership violation, authorization bypass, or lifetime primitive is established. The demonstrated consequence is low integrity impact to filesystem metadata persistence. A speculative consequence is limited file inconsistency after crash or power loss, but there is no plausible supported path to privilege escalation or memory corruption. ImportantCandidate=NO because the patch does not expose an Important-grade primitive. AutoDowngradeAllowed=YES because no unresolved corruption or security-boundary issue remains.

Likely operational severity is Low to ordinary Moderate.

5. One-sentence report phrase

ext2 IS_SYNC inode metadata updates could be lost because metadata sync was requested before the inode was marked dirty, allowing local authorized file or xattr changes to fail to persist after crash or power loss.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: this is a local filesystem metadata persistence bug without UAF, memory corruption, authorization bypass, network reachability, or privilege escalation evidence.

7. Call-site confidence

Call-site confidence: high

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

Patch: ext2: Fix lost inode updates for IS_SYNC inodes
Commit: 5efb3350230fef831167740e69e6db2861101186
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5efb3350230fef831167740e69e6db2861101186

Commit description:

ext2_setsize() and ext2_xattr_set2() had a construct like:

	if (IS_SYNC(inode)) {
		sync_inode_metadata(inode, 1);
	} else {
		mark_inode_dirty(inode);
	}

which leads to lost inode updates for IS_SYNC inodes because
sync_inode_metadata() does anything only if the inode is already dirty
and hence inode updates may be simply lost. Fix the problem by
unconditionally marking the inode dirty and *then* call
sync_inode_metadata().

CC: stable@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20260727104923.3828017-26-jack@suse.cz
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  fs/ext2/inode.c
  fs/ext2/xattr.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=5efb3350230fef831167740e69e6db2861101186

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

The original Linux kernel CVE announcement for CVE-2026-89601 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89601

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:L/UI:N/S:U/C:N/I:L/A:N
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:L
  The Best / paranoid CVSS score: 3.6

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: 2

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).