Bluetooth: Introduce trusted flag for management control sockets

Providing a global trusted flag for management control sockets provides
an easy way for identifying sockets and imposing restriction on it. For
now all management sockets are trusted since they require CAP_NET_ADMIN.
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>

include/net/bluetooth/hci.h

@@ -181,6 +181,7 @@ enum {
 
 /* HCI socket flags */
 enum {
+	HCI_SOCK_TRUSTED,
 	HCI_MGMT_INDEX_EVENTS,
 	HCI_MGMT_UNCONF_INDEX_EVENTS,
 	HCI_MGMT_EXT_INDEX_EVENTS,

net/bluetooth/hci_sock.c

@@ -796,6 +796,11 @@ static int hci_sock_bind(struct socket *sock, struct sockaddr *addr,
 			goto done;
 		}
 
+		/* The monitor interface is restricted to CAP_NET_RAW
+		 * capabilities and with that implicitly trusted.
+		 */
+		hci_sock_set_flag(sk, HCI_SOCK_TRUSTED);
+
 		send_monitor_replay(sk);
 
 		atomic_inc(&monitor_promisc);
@@ -817,6 +822,12 @@ static int hci_sock_bind(struct socket *sock, struct sockaddr *addr,
 			goto done;
 		}
 
+		/* Since the access to control channels is currently
+		 * restricted to CAP_NET_ADMIN capabilities, every
+		 * socket is implicitly trusted.
+		 */
+		hci_sock_set_flag(sk, HCI_SOCK_TRUSTED);
+
 		/* At the moment the index and unconfigured index events
 		 * are enabled unconditionally. Setting them on each
 		 * socket when binding keeps this functionality. They