[CVE-2026-46047][MODERATE 7.0] net: qrtr: ns: Fix use-after-free in driver remove()

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

CVE: CVE-2026-46047
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: net: qrtr: ns: Fix use-after-free in driver remove()
Commit: 0f313eb6a8f6dffa491373cf3afab979fa1c02f4
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0f313eb6a8f6dffa491373cf3afab979fa1c02f4
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46047
Analysis date: Wed, 27 May 2026 12:00:50 -0400
ActionableScore: 7
ActionableScore lower bound: 4
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A QRTR nameservice remove race can let `qrtr_ns_data_ready()` queue work after the workqueue is destroyed, creating a local teardown UAF with likely kernel crash and possible broader lifetime-corruption risk.

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

The original Linux kernel CVE announcement for CVE-2026-46047 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46047

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: MODERATE 7.0
Manual review required: YES

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
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CVE-2026-46047	MODERATE	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-362;*CWE-664;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A use after free can occur in QRTR nameservice removal if a packet arrives after the workqueue is destroyed but before the socket is released. The old sk data ready callback could still run and attempt to queue work or dereference nameservice state during teardown. For the CVSS the PR:L is used only in the paranoid score where a less privileged local actor can race QRTR traffic with service removal, rebind, hotplug, or delegated device management. The typical case is closer to PR:H because triggering removal normally requires administrative control. The issue is not network reachable in the normal IP sense and does not show an out of bounds write or arbitrary write. Impact is at least denial of service via kernel crash. Because this is a real teardown use after free, worst case confidentiality and integrity impact should be reviewed manually even though reliable exploitation is not demonstrated.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 6)	YES	UAF LINUS KPANIC PACKET 	NO	NO	checked

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

ActionableScore=7
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Generic memory corruption, strong corruption primitive: +2
  The commit explicitly describes a UAF caused by `qrtr_ns_data_ready()` using nameservice workqueue state after teardown.

* Real lifetime corruption: +1
  This is a teardown lifetime race between socket callback execution, RX processing, workqueue destruction, and socket release.

* Reliable kernel crash / strong DoS: +1
  A packet arriving in the teardown window can cause workqueue or work struct dereference after destruction.

* Privileged kernel/device-management memory corruption path: +1
  The UAF occurs in a subsystem remove path, a trusted kernel teardown context.

Subtracting signals:

* Requires administrative removal in typical deployments: -2
  Removing QRTR nameservice or driver state normally requires privileged device/module/subsystem management.

* Hard race / special timing required: -1
  A packet must arrive after `destroy_workqueue()` but before `sock_release()` or while RX threads still use the callback.

Paranoid additions:

* Local reduced-privilege trigger concern: +1
  A less privileged local actor may be able to generate QRTR traffic while another service, hotplug path, or delegated device-management flow triggers removal.

* Privilege escalation plausible: +2
  A real UAF in a socket callback and workqueue teardown path can sometimes be exploitable beyond crash if object lifetime and reclaim can be influenced, although no reliable primitive is shown.

* Confidentiality/integrity impact plausible: +1
  UAF may theoretically expose or corrupt stale kernel state if reclaim is controllable.

## 3. Reachability analysis

The realistic trigger requires QRTR nameservice removal or driver teardown while QRTR packets are still arriving. The removal side is typically privileged, but packet generation may be available to local clients on systems using QRTR.

Namespaces and containers matter if QRTR access or device-management operations are delegated to untrusted workloads. This is not network reachable in the normal IP sense. Practical exposure is platform-specific, mainly Qualcomm-style systems using QRTR.

## 4. Severity interpretation

This is stronger than an ordinary Moderate resource issue because it is a real UAF in teardown. Conservative impact is kernel crash/DoS under a narrow remove race.

The paranoid interpretation is a Strong Important candidate because socket-callback and workqueue teardown UAFs can sometimes become exploitable memory lifetime bugs. However, reliable LPE is not demonstrated and practical reachability is constrained.

## 5. One-sentence report phrase

A QRTR nameservice remove race can let `qrtr_ns_data_ready()` queue work after the workqueue is destroyed, creating a local teardown UAF with likely kernel crash and possible broader lifetime-corruption risk.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is a real UAF in a kernel socket callback and workqueue teardown path, even though practical triggering usually requires privileged removal plus a timing race.

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

Patch: net: qrtr: ns: Fix use-after-free in driver remove()
Commit: 0f313eb6a8f6dffa491373cf3afab979fa1c02f4
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0f313eb6a8f6dffa491373cf3afab979fa1c02f4

Commit description:

In the remove callback, if a packet arrives after destroy_workqueue() is
called, but before sock_release(), the qrtr_ns_data_ready() callback will
try to queue the work, causing use-after-free issue.

Fix this issue by saving the default 'sk_data_ready' callback during
qrtr_ns_init() and use it to replace the qrtr_ns_data_ready() callback at
the start of remove(). This ensures that even if a packet arrives after
destroy_workqueue(), the work struct will not be dereferenced.

Note that it is also required to ensure that the RX threads are completed
before destroying the workqueue, because the threads could be using the
qrtr_ns_data_ready() callback.

Cc: stable@vger.kernel.org
Fixes: 0c2204a ("net: qrtr: Migrate nameservice to kernel from userspace")
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>
Link: https://patch.msgid.link/20260409-qrtr-fix-v3-5-00a8a5ff2b51@oss.qualcomm.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/qrtr/ns.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=0f313eb6a8f6dffa491373cf3afab979fa1c02f4

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

The original Linux kernel CVE announcement for CVE-2026-46047 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46047

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: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: 4
  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: MODERATE
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): MODERATE 7.0

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).