[CVE-2026-46330][IMPORTANT] Revert "net/smc: Introduce TCP ULP support" [ Upstream

[CVE-2026-46330][IMPORTANT] Revert "net/smc: Introduce TCP ULP support" [ Upstream

[AL-KERNEL]

CVE: CVE-2026-46330
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: Revert "net/smc: Introduce TCP ULP support" [ Upstream
Commit: 6c505d95c69e27dbf28fea29dc84d2498d69515c
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6c505d95c69e27dbf28fea29dc84d2498d69515c
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46330
Analysis date: Tue, 09 Jun 2026 09:28:13 -0400
ActionableScore: 7
ActionableScore lower bound: 5
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
The SMC TCP ULP conversion path could let a local user trigger VFS and socket lifetime corruption by replacing an active TCP socket with an SMC socket in place, creating UAF risk and possible kernel crash or privilege escalation concerns.

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

The original Linux kernel CVE announcement for CVE-2026-46330 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46330

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: IMPORTANT
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-2026-46330	IMPORTANT	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:H/I:H/A:H';*CWE-416;*CWE-664;*CWE-672;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'The SMC TCP ULP implementation attempted to convert an already open TCP socket into an SMC socket by modifying the underlying struct file, private_data, inode, and dentry state in place. This violates VFS lifetime and identity assumptions for open files and can create use-after-free conditions or general kernel instability when later close, fput, dput, or socket paths operate on stale or mismatched objects. For the CVSS the PR:L is used because a local unprivileged process may be able to create a TCP socket and request the smc TCP ULP on its own file descriptor when the feature is available. The issue is not directly network reachable because the dangerous operation is a local socket control operation rather than remote packet processing. Impact is at least local denial of service via kernel crash, and in the paranoid interpretation it may allow confidentiality or integrity impact due to UAF style memory corruption and should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7)	YES	OOB INIT BPF UAF LINUS IPV6  KPANIC INCREASED_TO_MODERATE7_FROM_MODERATE_BASED_ON_GUESSCVSS KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7	NO	NO	checked

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

ActionableScore=7
ActionableScoreLower=5

## 1. ActionableScore

* Conservative score: 5
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1
  A local process can plausibly create a TCP socket and request the `smc` TCP ULP on its own file descriptor if the feature is available.

* Generic memory corruption: +2
  The reverted code modified `struct file`, `file->private_data`, `file->f_inode`, and `dentry->d_inode` in place for an already open socket. The commit explicitly calls out use after free risk and violation of VFS invariants.

* Real lifetime corruption: +1
  This is a lifetime and ownership violation involving VFS and socket objects, not just a validation error.

* Reliable kernel crash / strong DoS: +1
  The commit describes general system instability and UAF risk in core close/fput/dput/socket paths.

* Rare or configuration dependent subsystem: -1
  This requires SMC TCP ULP support to be present and usable. It is not a universal default networking receive path.

Conservative total: 5

Paranoid additional signals:

* Weak LPE concern: +1
  UAF style object lifetime corruption in VFS/socket structures can sometimes be shaped into privilege escalation, although no concrete reclaim or overwrite primitive is demonstrated in the patch.

* Confidentiality impact plausible: +1
  In the paranoid interpretation, stale or mismatched VFS/socket object access may expose unintended kernel object state, but this is not proven.

Paranoid total: 7

Not counted:

* Remote reachable: +0
  This is not triggered by remote packets directly.

* Strong LPE plausibility: +0
  The patch does not show attacker controlled reclaim, function pointer control, arbitrary write, refcount takeover, or a demonstrated exploitation primitive.

* Admin/root requirement penalty: +0
  The likely trigger is a local socket operation, not a CAP_SYS_ADMIN or CAP_NET_ADMIN only management path.

## 3. Reachability analysis

The realistic trigger is local. An attacker needs local code execution and the ability to create a TCP socket and enable the `smc` TCP ULP on it. This is PR:L in CVSS style reasoning, not PR:H, because the operation is tied to the attacker's own socket and does not obviously require full administrative control.

Namespaces or containers may matter because a reduced privilege container process or service account may still be able to create TCP sockets and exercise TCP ULP behavior if the host exposes this kernel feature. The bug is not network reachable in the sense of remote packet parsing.

The path is not a broad default TCP/IP data path. It depends on SMC TCP ULP support being built or loadable and registered. That lowers exposure, but the affected objects are core VFS and socket lifetime structures, which raises triage priority.

## 4. Severity interpretation

This is stronger than an ordinary Moderate because the reverted code violates core VFS object identity and lifetime assumptions for an already open file. The demonstrated impact is kernel instability or crash, but the underlying primitive is UAF style lifetime corruption rather than a simple NULL dereference or warning.

Realistic exploitation evidence for privilege escalation is limited. However, the affected structures are high value kernel objects and the design flaw is severe enough that the feature was removed entirely rather than fixed locally. This should be treated as Actionable Moderate at minimum, with a defensible paranoid classification as a Strong Important candidate.

## 5. One-sentence report phrase

The SMC TCP ULP conversion path could let a local user trigger VFS and socket lifetime corruption by replacing an active TCP socket with an SMC socket in place, creating UAF risk and possible kernel crash or privilege escalation concerns.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

This is a core object lifetime violation involving `struct file`, inode, dentry, and socket state. Even without a demonstrated exploit primitive, the UAF risk and possible LPE implications are strong enough that it should not be auto-closed.

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

Patch: Revert "net/smc: Introduce TCP ULP support" [ Upstream
Commit: 6c505d95c69e27dbf28fea29dc84d2498d69515c
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6c505d95c69e27dbf28fea29dc84d2498d69515c

Changed files:
  net/smc/af_smc.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=6c505d95c69e27dbf28fea29dc84d2498d69515c

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

The original Linux kernel CVE announcement for CVE-2026-46330 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46330

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:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 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: 5
  Paranoid ActionableScore: 7

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: IMPORTANT
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): IMPORTANT

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).