[CVE-2026-68378][LOW] dpll: fix NULL pointer dereference in dpll_msg_add_pin_ref_sync()

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

CVE: CVE-2026-68378
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: dpll: fix NULL pointer dereference in dpll_msg_add_pin_ref_sync()
Commit: 66fbe0499ef517ab161b96c49886a891851f6481
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=66fbe0499ef517ab161b96c49886a891851f6481
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68378
Analysis date: Mon, 10 Aug 2026 11:52:26 -0400
ActionableScore: 1
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like auto-close candidate
Manual review required: NO

Summary:
A NULL pointer dereference in the dpll netlink notification path can occur during dpll pin unregister when a shared ref_sync partner remains registered on another dpll device but no longer has private state for the current device, causing a local privileged denial of service.

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

The original Linux kernel CVE announcement for CVE-2026-68378 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68378

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.

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AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-68378	LOW	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:N/A:H';**CWE-476;CWE-754;*CWE-664;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'A NULL pointer dereference in the dpll netlink notification path can occur during dpll device and pin unregistration when a shared pin still exists on another dpll device but has already been removed from the current devices pin_refs. In that state dpll_msg_add_pin_ref_sync() can find the ref_sync partner in ref_sync_pins and pass the availability check, but dpll_pin_on_dpll_priv() returns NULL for the current dpll device. The NULL private pointer is then passed into the driver ref_sync_get callback and can crash the kernel. For the CVSS the PR:L is used in the paranoid score because a reduced capability administrator, container root, service account, or delegated device management context may be able to trigger driver removal or device unregister flows, although typical module removal still requires administrative control. The issue is not network reachable and requires local control over the affected dpll device lifecycle. Impact is denial of service via kernel crash.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like auto-close candidate (with actual score 1)	YES	DANGER NULLPTR INIT HARDWARE  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=1
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate / Low-like auto-close candidate**

## 2. Signal breakdown

Conservative signals:

* Reliable kernel crash / strong DoS: +1. The commit shows a concrete NULL pointer dereference in `zl3073x_dpll_input_pin_ref_sync_get()` through `dpll_msg_add_pin_ref_sync()`.
* Requires admin/root/CAP in typical deployments: -2. The realistic trigger is dpll device or driver unregister, commonly during driver module removal or device teardown, which is normally administrative.
* Rare and difficult-to-reach subsystem/configuration: -1. The bug requires shared `dpll_pin` objects across multiple `dpll_device` instances, ref_sync pairs, and a specific unregister ordering.

Conservative score is floored at 0.

Paranoid adjustment:

* Do not apply full -2 privilege penalty if the environment has delegated device management, service accounts, container root, or reduced-capability admin flows able to trigger device unregister. This raises the practical score to 1.
* No memory corruption score is added. The provided trace and patch support NULL dereference only, not UAF, stale reuse, arbitrary write, type confusion, or refcount takeover.
* No confidentiality or integrity impact is counted.

## 3. Reachability analysis

The bug is local and lifecycle-triggered. A typical attacker would need the ability to unload or remove an affected dpll driver or otherwise trigger dpll pin/device unregister paths. It is not network reachable. Namespace or container impact depends on whether a container or service account has delegated control over the affected device lifecycle, but ordinary unprivileged users normally cannot trigger this path. The affected configuration is also relatively specific because it requires shared dpll pins with ref_sync relationships across multiple dpll devices.

Call-site confidence: high. The patch and trace show the direct failing call path and the exact missing NULL check before `ops->ref_sync_get()`.

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like local DoS, not an Important-class kernel vulnerability. The realistic impact is a kernel Oops/crash during device unregister. Theoretical memory-corruption or privilege-escalation impact is not supported by the patch because the failing pointer is NULL and the fix only skips ref_sync pins whose per-device private pointer cannot be resolved.

## 5. One-sentence report phrase

A NULL pointer dereference in the dpll netlink notification path can occur during dpll pin unregister when a shared ref_sync partner remains registered on another dpll device but no longer has private state for the current device, causing a local privileged denial of service.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This can be auto-closed for practical triage unless the affected product delegates dpll device removal or driver lifecycle control to untrusted local users. No network reachability, UAF, arbitrary write, or plausible LPE primitive is evident.

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

Patch: dpll: fix NULL pointer dereference in dpll_msg_add_pin_ref_sync()
Commit: 66fbe0499ef517ab161b96c49886a891851f6481
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=66fbe0499ef517ab161b96c49886a891851f6481

Commit description:

When a dpll_pin is shared across multiple dpll_device instances and
those devices are being unregistered (e.g. during driver module removal),
a NULL pointer dereference can occur in dpll_msg_add_pin_ref_sync().

This happens under the following conditions:
 - A pin is registered with two or more dpll devices (dpll_A, dpll_B)
 - The pin has ref_sync pairs with other pins
 - During unregistration of dpll_A's pins, a ref_sync partner pin is
   unregistered first, removing it from dpll_A->pin_refs
 - But since the partner pin is still registered with dpll_B, its
   dpll_refs is not empty, so dpll_pin_ref_sync_pair_del() does NOT
   run and the partner stays in the pin's ref_sync_pins xarray
 - When the pin itself is then unregistered from dpll_A, the delete
   notification calls dpll_msg_add_pin_ref_sync() which finds the
   partner in ref_sync_pins, passes dpll_pin_available() (partner is
   still registered with dpll_B), but dpll_pin_on_dpll_priv(dpll_A,
   partner) returns NULL because partner was already removed from
   dpll_A->pin_refs
 - The NULL priv pointer is passed to the driver's ref_sync_get
   callback, which dereferences it

 BUG: kernel NULL pointer dereference, address: 0000000000000034
 Oops: Oops: 0000 [#1] SMP NOPTI
 RIP: 0010:zl3073x_dpll_input_pin_ref_sync_get+0x73/0x80 [zl3073x]
 Call Trace:
  dpll_msg_add_pin_ref_sync+0xb8/0x200
  dpll_cmd_pin_get_one+0x3b6/0x4b0
  dpll_pin_event_send+0x72/0x140
  __dpll_pin_unregister+0x5a/0x2b0
  dpll_pin_unregister+0x49/0x70

Fix this by skipping ref_sync pins whose priv pointer cannot be resolved
for the current dpll device.

Fixes: 58256a2 ("dpll: add reference sync get/set")
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Link: https://patch.msgid.link/20260710193625.1378822-1-ivecera@redhat.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/dpll/dpll_netlink.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=66fbe0499ef517ab161b96c49886a891851f6481

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

The original Linux kernel CVE announcement for CVE-2026-68378 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68378

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:H
  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: 0
  Paranoid ActionableScore: 1

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.
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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).