net: qrtr: Allocate workqueue before kernel_bind

A null pointer dereference in qrtr_ns_data_ready() is seen if a client
opens a qrtr socket before qrtr_ns_init() can bind to the control port.
When the control port is bound, the ENETRESET error will be broadcasted
and clients will close their sockets. This results in DEL_CLIENT
packets being sent to the ns and qrtr_ns_data_ready() being called
without the workqueue being allocated.

Allocate the workqueue before setting sk_data_ready and binding to the
control port. This ensures that the work and workqueue structs are
allocated and initialized before qrtr_ns_data_ready can be called.

Fixes: 0c2204a4 ("net: qrtr: Migrate nameservice to kernel from userspace")
Signed-off-by: Chris Lew <clew@codeaurora.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/qrtr/ns.c

@@ -712,6 +712,10 @@ void qrtr_ns_init(void)
 		goto err_sock;
 	}
 
+	qrtr_ns.workqueue = alloc_workqueue("qrtr_ns_handler", WQ_UNBOUND, 1);
+	if (!qrtr_ns.workqueue)
+		goto err_sock;
+
 	qrtr_ns.sock->sk->sk_data_ready = qrtr_ns_data_ready;
 
 	sq.sq_port = QRTR_PORT_CTRL;
@@ -720,17 +724,13 @@ void qrtr_ns_init(void)
 	ret = kernel_bind(qrtr_ns.sock, (struct sockaddr *)&sq, sizeof(sq));
 	if (ret < 0) {
 		pr_err("failed to bind to socket\n");
-		goto err_sock;
+		goto err_wq;
 	}
 
 	qrtr_ns.bcast_sq.sq_family = AF_QIPCRTR;
 	qrtr_ns.bcast_sq.sq_node = QRTR_NODE_BCAST;
 	qrtr_ns.bcast_sq.sq_port = QRTR_PORT_CTRL;
 
-	qrtr_ns.workqueue = alloc_workqueue("qrtr_ns_handler", WQ_UNBOUND, 1);
-	if (!qrtr_ns.workqueue)
-		goto err_sock;
-
 	ret = say_hello(&qrtr_ns.bcast_sq);
 	if (ret < 0)
 		goto err_wq;