[CVE-2022-50835][LOW] jbd2: add miss release buffer head in fc_do_one_pass()

[CVE-2022-50835][LOW] jbd2: add miss release buffer head in fc_do_one_pass()

[AL-KERNEL]

CVE: CVE-2022-50835
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: jbd2: add miss release buffer head in fc_do_one_pass()
Commit: e65506ff181fc176088f32117d69b9cb1ddda777
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e65506ff181fc176088f32117d69b9cb1ddda777
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2022-50835
Analysis date: Wed, 20 May 2026 22:38:56 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
jbd2 fast commit replay missed a brelse call after processing a buffer_head, causing a recovery-path reference leak with limited availability impact and no demonstrated memory corruption primitive.

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

The original Linux kernel CVE announcement for CVE-2022-50835 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2022-50835

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-2022-50835	LOW	CHECK	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-772;*CWE-401;*CWE-664;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'jbd2 fast commit replay missed a brelse call after using a buffer_head in fc_do_one_pass, causing a reference leak during journal recovery. This is a recovery path resource leak rather than a UAF or overwrite primitive, and the patch does not indicate page cache corruption or privilege escalation. For the CVSS the PR:L is used only in the paranoid score for environments where a local user can influence filesystem recovery through delegated mount or supplied disk image access. In typical deployments PR:H is more realistic because mounting or replaying a journal requires administrator control. The issue is not network reachable. Impact is mainly availability through leaked buffer_head references under recovery conditions.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)	YES	DISK SIMPLEFIX LEAK CVEOUTDATED 	NO	YES	checked

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

ActionableScore=2

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**::

## 2. Signal breakdown

Triggered signals:

* Important filesystem/storage path: +1. The bug is in jbd2 fast commit journal recovery, which is relevant to ext4/journal recovery correctness.
* Broad/default/common subsystem: +1 in the paranoid score. jbd2/ext4 is widely deployed, although this exact path is limited to fast commit replay.
* Availability impact realistic: +1. A missing brelse can leak buffer_head references during replay and may degrade recovery or resource usage if repeated.
* Requires admin/root/CAP_SYS_ADMIN in typical deployments: -2. Triggering journal recovery normally requires mounting or recovering a filesystem, which is privileged.
* Rare or difficult-to-reach condition: -1. The issue is limited to fast commit replay and only leaks one buffer_head reference per processed fast commit block path.

Not triggered:

* No remote reachability.
* No local unprivileged trigger in normal deployments.
* No generic memory corruption. This is a reference leak, not UAF, double free, OOB write, page-cache corruption, or arbitrary write.
* No privilege escalation plausibility from the patch.
* No strong immediate kernel crash shown.

## 3. Reachability analysis

In typical deployments, the affected path is reached during jbd2 fast commit recovery, usually as part of mounting or replaying an ext4 journal. That operation is normally controlled by root or a privileged system service.

Containers or namespaces only change the privilege assessment if untrusted users can cause the host to mount or recover attacker-supplied ext4 images. Without such delegation, this is not directly reachable by an unprivileged user.

The path is not network reachable and is not part of ordinary file I/O after the filesystem is mounted. Realistic exploitation is limited to recovery-time resource leakage, not active memory corruption.

## 4. Severity interpretation

This behaves like a Low-like or ordinary Moderate issue. The practical impact is a buffer_head reference leak in a filesystem recovery path.

Theoretical impact is limited to resource retention and possible recovery degradation. The patch does not support UAF, controlled overwrite, page-cache corruption, information disclosure, or privilege escalation. Even under a paranoid model with attacker-supplied filesystem images, the issue remains primarily an availability/resource leak concern.

## 5. One-sentence report phrase

jbd2 fast commit replay missed a brelse call after processing a buffer_head, causing a recovery-path reference leak with limited availability impact and no demonstrated memory corruption primitive.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: this is a simple missing reference release in a privileged journal recovery path, with no remote trigger, no unprivileged default trigger, and no evidence of UAF or overwrite-based memory corruption.

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

Patch: jbd2: add miss release buffer head in fc_do_one_pass()
Commit: e65506ff181fc176088f32117d69b9cb1ddda777
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e65506ff181fc176088f32117d69b9cb1ddda777

Commit description:

In fc_do_one_pass() miss release buffer head after use which will lead
to reference count leak.

Cc: stable@kernel.org
Signed-off-by: Ye Bin <yebin10@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20220917093805.1782845-1-yebin10@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  fs/jbd2/recovery.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=e65506ff181fc176088f32117d69b9cb1ddda777

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

The original Linux kernel CVE announcement for CVE-2022-50835 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2022-50835

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: 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).