ksmbd: add max ip connections parameter

commit d8b6dc9 upstream.

This parameter set the maximum number of connections per ip address.
The default is 8.

Cc: stable@vger.kernel.org
Fixes: c0d4111 ("ksmbd: extend the connection limiting mechanism to support IPv6")
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: namjaejeon

fs/smb/server/ksmbd_netlink.h

@@ -112,10 +112,11 @@ struct ksmbd_startup_request {
 	__u32	smbd_max_io_size;	/* smbd read write size */
 	__u32	max_connections;	/* Number of maximum simultaneous connections */
 	__s8	bind_interfaces_only;
-	__s8	reserved[503];		/* Reserved room */
+	__u32	max_ip_connections;	/* Number of maximum connection per ip address */
+	__s8	reserved[499];		/* Reserved room */
 	__u32	ifc_list_sz;		/* interfaces list size */
 	__s8	____payload[];
-};
+} __packed;
 
 #define KSMBD_STARTUP_CONFIG_INTERFACES(s)	((s)->____payload)
 

fs/smb/server/server.h

@@ -43,6 +43,7 @@ struct ksmbd_server_config {
 	unsigned int		auth_mechs;
 	unsigned int		max_connections;
 	unsigned int		max_inflight_req;
+	unsigned int		max_ip_connections;
 
 	char			*conf[SERVER_CONF_WORK_GROUP + 1];
 	struct task_struct	*dh_task;

fs/smb/server/transport_ipc.c

@@ -335,6 +335,9 @@ static int ipc_server_config_on_startup(struct ksmbd_startup_request *req)
 	if (req->max_connections)
 		server_conf.max_connections = req->max_connections;
 
+	if (req->max_ip_connections)
+		server_conf.max_ip_connections = req->max_ip_connections;
+
 	ret = ksmbd_set_netbios_name(req->netbios_name);
 	ret |= ksmbd_set_server_string(req->server_string);
 	ret |= ksmbd_set_work_group(req->work_group);

fs/smb/server/transport_tcp.c

@@ -240,6 +240,7 @@ static int ksmbd_kthread_fn(void *p)
 	struct interface *iface = (struct interface *)p;
 	struct ksmbd_conn *conn;
 	int ret;
+	unsigned int max_ip_conns;
 
 	while (!kthread_should_stop()) {
 		mutex_lock(&iface->sock_release_lock);
@@ -257,34 +258,38 @@ static int ksmbd_kthread_fn(void *p)
 			continue;
 		}
 
+		if (!server_conf.max_ip_connections)
+			goto skip_max_ip_conns_limit;
+
 		/*
 		 * Limits repeated connections from clients with the same IP.
 		 */
+		max_ip_conns = 0;
 		down_read(&conn_list_lock);
-		list_for_each_entry(conn, &conn_list, conns_list)
+		list_for_each_entry(conn, &conn_list, conns_list) {
 #if IS_ENABLED(CONFIG_IPV6)
 			if (client_sk->sk->sk_family == AF_INET6) {
 				if (memcmp(&client_sk->sk->sk_v6_daddr,
-					   &conn->inet6_addr, 16) == 0) {
-					ret = -EAGAIN;
-					break;
-				}
+					   &conn->inet6_addr, 16) == 0)
+					max_ip_conns++;
 			} else if (inet_sk(client_sk->sk)->inet_daddr ==
-				 conn->inet_addr) {
-				ret = -EAGAIN;
-				break;
-			}
+				 conn->inet_addr)
+				max_ip_conns++;
 #else
 			if (inet_sk(client_sk->sk)->inet_daddr ==
-			    conn->inet_addr) {
+			    conn->inet_addr)
+				max_ip_conns++;
+#endif
+			if (server_conf.max_ip_connections <= max_ip_conns) {
 				ret = -EAGAIN;
 				break;
 			}
-#endif
+		}
 		up_read(&conn_list_lock);
 		if (ret == -EAGAIN)
 			continue;
 
+skip_max_ip_conns_limit:
 		if (server_conf.max_connections &&
 		    atomic_inc_return(&active_num_conn) >= server_conf.max_connections) {
 			pr_info_ratelimited("Limit the maximum number of connections(%u)\n",