ksmbd: smbd: fix kernel oops during server shutdown

if server shutdown happens in the situation that
there are connections, workqueue could be destroyed
before queueing disconnect work.
Signed-off-by: Hyunchul Lee <hyc.lee@gmail.com>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/ksmbd/transport_rdma.c

@@ -329,6 +329,7 @@ static void smb_direct_disconnect_rdma_work(struct work_struct *work)
 static void
 smb_direct_disconnect_rdma_connection(struct smb_direct_transport *t)
 {
+	if (t->status == SMB_DIRECT_CS_CONNECTED)
 		queue_work(smb_direct_wq, &t->disconnect_work);
 }
 
@@ -1415,7 +1416,7 @@ static void smb_direct_disconnect(struct ksmbd_transport *t)
 
 	ksmbd_debug(RDMA, "Disconnecting cm_id=%p\n", st->cm_id);
 
-	smb_direct_disconnect_rdma_connection(st);
+	smb_direct_disconnect_rdma_work(&st->disconnect_work);
 	wait_event_interruptible(st->wait_status,
 				 st->status == SMB_DIRECT_CS_DISCONNECTED);
 	free_transport(st);