[PATCH net] net: qrtr: restrict socket creation to the initial network namespace

[Aldo Ariel Panzardo <qwe.aldo@gmail.com>]

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>
---
 net/qrtr/af_qrtr.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/qrtr/af_qrtr.c b/net/qrtr/af_qrtr.c
index d02ef9a74c3c..a30fa56e6aa3 100644
--- a/net/qrtr/af_qrtr.c
+++ b/net/qrtr/af_qrtr.c
@@ -1263,6 +1263,14 @@ static int qrtr_create(struct net *net, struct socket *sock,
 	if (sock->type != SOCK_DGRAM)
 		return -EPROTOTYPE;
 
+	/* QRTR keeps its port and node state in module-global variables that
+	 * are not partitioned per network namespace, and the in-kernel name
+	 * service only operates in init_net. Confine the family to init_net so
+	 * a socket in another namespace cannot reach the global control plane.
+	 */
+	if (!net_eq(net, &init_net))
+		return -EAFNOSUPPORT;
+
 	sk = sk_alloc(net, AF_QIPCRTR, GFP_KERNEL, &qrtr_proto, kern);
 	if (!sk)
 		return -ENOMEM;
-- 
2.43.0