[CVE-2026-46196][LOW] tracepoint: balance regfunc() on func_add() failure in tracepoint_add_func() [ Upstream

[CVE-2026-46196][LOW] tracepoint: balance regfunc() on func_add() failure in tracepoint_add_func() [ Upstream

[AL-KERNEL]

CVE: CVE-2026-46196
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: tracepoint: balance regfunc() on func_add() failure in tracepoint_add_func() [ Upstream
Commit: 247ed8a969f981bfba3112fd4bb441eaa6cef59c
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=247ed8a969f981bfba3112fd4bb441eaa6cef59c
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46196
Analysis date: Thu, 28 May 2026 05:55:39 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A tracepoint registration error path can leave `regfunc()` side effects active after `func_add()` failure, causing persistent local syscall tracing overhead and availability degradation until reboot.

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

The original Linux kernel CVE announcement for CVE-2026-46196 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46196

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-2026-46196	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-459;*CWE-772;**CWE-400;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'tracepoint_add_func can call a tracepoint regfunc during first probe registration and then fail in func_add under memory pressure, leaving the regfunc side effects active without an installed probe. For syscall tracepoints this can leave syscall tracing state enabled and force ongoing syscall entry and exit overhead until reboot, creating a persistent local denial of service condition. For the CVSS the PR:L is used for the paranoid score because some deployments may expose perf or tracing style tracepoint registration to non admin local users or delegated service contexts, although typical systems restrict this to privileged users. The issue is not network reachable and does not provide evidence of memory corruption, information disclosure, or privilege escalation. Impact is availability only through persistent tracing overhead and leaked subsystem state.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)	YES	TRACE SIMPLEFIX LEAK ERRORPATH LINUS BOOT 	NO	NO	checked

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

ActionableScore=2
ActionableScoreLower=1

## 1. ActionableScore

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

## 2. Signal breakdown

* **Availability impact realistic: +1**
  A failed `func_add()` after `regfunc()` can leave persistent tracepoint side effects active. For syscall tracepoints this can keep syscall tracepoint state enabled and impose ongoing syscall entry and exit overhead until reboot.

* **Local unprivileged trigger, paranoid only: +1**
  Typical systems restrict tracepoint registration through tracing, perf, or BPF related paths, but some deployments may expose limited tracing or perf functionality to non admin local users or delegated service contexts.

* **Broad/default/common subsystem, paranoid only: +1**
  Tracepoints are a core kernel instrumentation mechanism and syscall tracepoints can affect all tasks once enabled.

* **Hard or unreliable condition: -1**
  The problematic path requires `func_add()` failure after `regfunc()`, commonly an allocation failure such as `ENOMEM`, so reliable triggering is not straightforward.

* **Requires admin/root/CAP style privileges in typical deployments: -1 to -2**
  Conservative interpretation treats this as privileged tracing control. Paranoid interpretation reduces the penalty because some systems may delegate perf or tracing access, but this is still not a normal remote or unauthenticated path.

No UAF, double free, OOB write, arbitrary write, info leak, or privilege escalation primitive is indicated by the patch.

## 3. Reachability analysis

The bug is triggered during tracepoint probe registration, specifically on the first 0 to 1 transition when `regfunc()` succeeds but `func_add()` fails. In typical deployments this requires privileged access to tracing, perf, BPF, or related kernel instrumentation interfaces. Containers or namespaces only matter if such tracing capabilities or perf access are delegated. The issue is not network reachable. Realistic exploitation also needs an allocation failure or similar `func_add()` failure at the correct point, making the trigger less reliable.

## 4. Severity interpretation

This behaves like a cleanup imbalance causing persistent local DoS overhead, not like an Important class vulnerability. The realistic impact is availability degradation due to leaked tracepoint subsystem state. Theoretical memory corruption potential is not supported by the patch, and there is no evidence of confidentiality impact, integrity impact, or privilege escalation.

## 5. One-sentence report phrase

A tracepoint registration error path can leave `regfunc()` side effects active after `func_add()` failure, causing persistent local syscall tracing overhead and availability degradation until reboot.

## 6. Manual review recommendation

**NO MANUAL CHECK NEEDED**

This is a local cleanup/resource state leak with difficult triggering and no memory corruption, privilege escalation, or remote reachability evidence.

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

Patch: tracepoint: balance regfunc() on func_add() failure in tracepoint_add_func() [ Upstream
Commit: 247ed8a969f981bfba3112fd4bb441eaa6cef59c
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=247ed8a969f981bfba3112fd4bb441eaa6cef59c

Changed files:
  kernel/tracepoint.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=247ed8a969f981bfba3112fd4bb441eaa6cef59c

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

The original Linux kernel CVE announcement for CVE-2026-46196 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46196

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: 1
  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).