net: qrtr: fix null-ptr-deref in qrtr_ns_remove

A null-ptr-deref bug is reported by Hulk Robot like this:
--------------
KASAN: null-ptr-deref in range [0x0000000000000128-0x000000000000012f]
Call Trace:
qrtr_ns_remove+0x22/0x40 [ns]
qrtr_proto_fini+0xa/0x31 [qrtr]
__x64_sys_delete_module+0x337/0x4e0
do_syscall_64+0x34/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x468ded
--------------

When qrtr_ns_init fails in qrtr_proto_init, qrtr_ns_remove which would
be called later on would raise a null-ptr-deref because qrtr_ns.workqueue
has been destroyed.

Fix it by making qrtr_ns_init have a return value and adding a check in
qrtr_proto_init.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Qinglang Miao <miaoqinglang@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/qrtr/ns.c

@@ -755,7 +755,7 @@ static void qrtr_ns_data_ready(struct sock *sk)
 	queue_work(qrtr_ns.workqueue, &qrtr_ns.work);
 }
 
-void qrtr_ns_init(void)
+int qrtr_ns_init(void)
 {
 	struct sockaddr_qrtr sq;
 	int ret;
@@ -766,7 +766,7 @@ void qrtr_ns_init(void)
 	ret = sock_create_kern(&init_net, AF_QIPCRTR, SOCK_DGRAM,
 			       PF_QIPCRTR, &qrtr_ns.sock);
 	if (ret < 0)
-		return;
+		return ret;
 
 	ret = kernel_getsockname(qrtr_ns.sock, (struct sockaddr *)&sq);
 	if (ret < 0) {
@@ -797,12 +797,13 @@ void qrtr_ns_init(void)
 	if (ret < 0)
 		goto err_wq;
 
-	return;
+	return 0;
 
 err_wq:
 	destroy_workqueue(qrtr_ns.workqueue);
 err_sock:
 	sock_release(qrtr_ns.sock);
+	return ret;
 }
 EXPORT_SYMBOL_GPL(qrtr_ns_init);
 

net/qrtr/qrtr.c

@@ -1287,13 +1287,19 @@ static int __init qrtr_proto_init(void)
 		return rc;
 
 	rc = sock_register(&qrtr_family);
-	if (rc) {
-		proto_unregister(&qrtr_proto);
-		return rc;
-	}
+	if (rc)
+		goto err_proto;
 
-	qrtr_ns_init();
+	rc = qrtr_ns_init();
+	if (rc)
+		goto err_sock;
 
+	return 0;
+
+err_sock:
+	sock_unregister(qrtr_family.family);
+err_proto:
+	proto_unregister(&qrtr_proto);
 	return rc;
 }
 postcore_initcall(qrtr_proto_init);

net/qrtr/qrtr.h

@@ -29,7 +29,7 @@ void qrtr_endpoint_unregister(struct qrtr_endpoint *ep);
 
 int qrtr_endpoint_post(struct qrtr_endpoint *ep, const void *data, size_t len);
 
-void qrtr_ns_init(void);
+int qrtr_ns_init(void);
 
 void qrtr_ns_remove(void);