net: qrtr: restrict socket creation to the initial network namespace

net: qrtr: restrict socket creation to the initial network namespace

QRTR keeps its entire port and node state in module-global variables
that are not partitioned per network namespace: qrtr_local_nid is a
single global node id (always 1) and qrtr_ports is a single global
xarray. qrtr_port_lookup() and qrtr_local_enqueue() operate on that
global state with no network-namespace check, and qrtr_create() places
no restriction on the namespace a socket is created in.

As a result an unprivileged process that creates an AF_QIPCRTR socket
in a separate network namespace, e.g. via
unshare(CLONE_NEWUSER | CLONE_NEWNET), can send QRTR datagrams -
including control-plane messages such as QRTR_TYPE_NEW_SERVER - to QRTR
sockets owned by another namespace, and vice versa. The receiving
socket sees such a message as coming from node id 1, indistinguishable
from a legitimate local client, breaking the isolation that network
namespaces are expected to provide.

QRTR is a transport to global hardware endpoints (the modem and other
remote processors) and has no per-namespace semantics; its in-kernel
name service already creates its socket in init_net only. Confine the
socket family to the initial network namespace, as other
non-namespace-aware socket families do (see llc_ui_create() and the
ieee802154 socket code).

Fixes: bdabad3e363d ("net: Add Qualcomm IPC router")
Signed-off-by: Aldo Ariel Panzardo <qwe.aldo@gmail.com>
Link: https://patch.msgid.link/20260716154319.3297699-1-qwe.aldo@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>