[CVE-2026-80983][LOW] net/smc: fix socket refcount leak in smc_switch_conns()

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-80983
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: net/smc: fix socket refcount leak in smc_switch_conns()
Commit: 84dea0585f6b538ae895a8b1d025f4897737f3b1
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=84dea0585f6b538ae895a8b1d025f4897737f3b1
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80983
Analysis date: Fri, 11 Sep 2026 17:08:58 -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-2026-80983 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80983

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-2026-80983	LOW	https://www.kernelcve.org/list/?q=CVE-2026-80983 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-772;*CWE-401;**CWE-400;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'smc_switch_conns() can leak a socket reference when smc_cdc_get_free_slot() fails after sock_hold() has already been taken. The leaked sk_refcnt prevents smc_sock destruction, keeps send and receive buffers allocated, and may keep a network namespace reference alive so netns teardown can hang. For the CVSS the PR:L is used because a local user or process can create SMC sockets, while reliable triggering also depends on link failover or connection kill timing. The issue is not directly network reachable by ordinary packet traffic, although it affects a networking subsystem and may involve SMC peers in an internal RDMA or ISM environment. Impact is denial of service through resource leakage and namespace teardown blockage, with no supported UAF, OOB access, information leak, or privilege escalation primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)	YES	LOCK RACE LEAK ERRORPATH HARDWARE LINUS 	NO	NO	checked

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

ActionableScore=2
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 2
* Conservative score: 2. No floor or cap applied.
* Raw paranoid score: 2
* Paranoid score: 2. No floor or cap applied.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

Positive signals:

* +1 Concrete persistent kernel resource/reference leak. `sock_hold(&smc->sk)` is not matched by `sock_put()` on the `smc_cdc_get_free_slot()` error path.
* +1 Persistent availability/cleanup impact. The leaked `sk_refcnt` prevents `smc_sock` destruction, keeps socket buffers allocated, and may keep a network namespace reference alive so netns teardown cannot complete.

Non-awarded signals:

* RealUAF not awarded. This is a missing `sock_put()` reference leak, not a dangling post-free use.
* Concrete repeated release/refcount not awarded. The bug is missing release, not a second release on the same potentially freed reference.
* Strong LPE or weak LPE not awarded. No controlled reclaim, arbitrary write, callback control, credential manipulation, or security-boundary bypass is established.
* Confidentiality and integrity not awarded. The patch supports resource leakage and DoS only.
* Remote reachability not awarded. Ordinary packet traffic does not directly trigger the vulnerable path.
* Extra availability not awarded beyond the persistent resource/netns teardown impact already counted.
* Race/timing penalty not applied. The path depends on failover or connection kill during switching, but the supplied evidence does not prove a narrow attacker-uncontrollable race sufficient for a scoring penalty.
* Rare subsystem penalty not applied. SMC deployment is specialized, but the prompt requires concrete evidence before subtracting for niche exposure.

Repeated-release/refcount checklist:

* First release can end lifetime: not applicable.
* Exact same reference survives to second release: no.
* Second operation is a real lifetime/refcount mutation: no.
* +1 Concrete repeated release/refcount awarded: no.
* Paranoid repeated-refcount leverage +1 awarded: no.
* FLOOR 5 applied: no.

3. Reachability analysis

A local user or process can create SMC sockets in an environment where SMC is enabled and configured, so host-admin-equivalent privilege is not positively required for the affected user socket itself. Reliable triggering still depends on `smc_switch_conns()` running during link failover and on `smc_cdc_get_free_slot()` failing because the target link goes down or the connection is killed while switching is in progress. The supplied evidence does not establish direct remote packet-triggerability.

No complete namespace-scoped privilege chain is established. The bug can keep a network namespace reference alive, but the mere involvement of netns teardown does not show that a namespace-local capability controls the full vulnerable sequence. Prior setup of SMC-capable infrastructure may be required in practice, but that is deployment exposure rather than proof that the attacker must be host admin.

4. Primitive and severity interpretation

The exact primitive is a persistent socket reference leak caused by a missing `sock_put()` on one error path after `sock_hold()` has already incremented the socket reference count. This is not active structured UAF and not fixed stale storage UAF. It is a resource/lifetime leak with demonstrated consequences of retained socket buffers and blocked network namespace teardown.

PrimitiveClass is CLASS_C because the demonstrated behavior is DoS/resource-retention behavior without an independently useful corruption primitive. ImportantCandidate is NO because there is no UAF, double release, memory corruption, authorization bypass, controlled reclaim, or C/I impact. AutoDowngradeAllowed is YES because the issue is suitable for ordinary Moderate handling and does not contain unresolved Important-grade exploitation leverage.

5. One-sentence report phrase

A missing sock_put() in the smc_switch_conns() error path can leak SMC socket references during link failover, preventing socket and netns cleanup and causing denial of service through persistent resource retention.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

The issue is a concrete reference/resource leak with DoS impact only, and the patch does not establish UAF, repeated release, memory corruption, authorization bypass, or privilege escalation.

7. Call-site confidence

Call-site confidence: high

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

Patch: net/smc: fix socket refcount leak in smc_switch_conns()
Commit: 84dea0585f6b538ae895a8b1d025f4897737f3b1
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=84dea0585f6b538ae895a8b1d025f4897737f3b1

Commit description:

smc_switch_conns() takes a reference on the SMC socket before dropping
lgr->conns_lock, so the connection stays alive while the CDC slot is
fetched:

        sock_hold(&smc->sk);
        read_unlock_bh(&lgr->conns_lock);
        /* pre-fetch buffer outside of send_lock, might sleep */
        rc = smc_cdc_get_free_slot(conn, to_lnk, &wr_buf, NULL, &pend);
        if (rc)
                goto err_out;

The err_out label only drops the wr_tx link reference, so this early exit
returns without the matching sock_put(). The second error exit is not
affected, because sock_put() has already run by then.

A leaked sk_refcnt means the smc_sock is never destroyed. Its send and
receive buffers stay allocated, and for a user socket the reference held
on the network namespace is never released, so the netns can no longer be
torn down.

smc_cdc_get_free_slot() fails when the target link goes down or when the
connection has been killed while the switch is in progress. Both are
reachable during the link failover this function implements, so the leak
is triggered by the same hardware events that make smc_switch_conns() run
in the first place.

Restructure so there is a single sock_put() covering both outcomes,
instead of adding a second one to the error path.

Fixes: 95f7f3e ("net/smc: improved fix wait on already cleared link")
Cc: stable@vger.kernel.org
Reviewed-by: Mahanta Jambigi <mjambigi@linux.ibm.com>
Reviewed-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Hidayath Khan <hidayath@linux.ibm.com>
Link: https://patch.msgid.link/20260820144729.1019399-1-hidayath@linux.ibm.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/smc/smc_core.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=84dea0585f6b538ae895a8b1d025f4897737f3b1

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

The original Linux kernel CVE announcement for CVE-2026-80983 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80983

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: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).