Properly initialize the message lists.

The message lists are implemented using a TAILQ from queue(3).  The heads
of the list must be initialized using the provided macros, since the field
called 'tqh_last' is non-zero in the initial state.  This patch fixes a
potential null pointer dereference by properly initializing the queues.

Note that there is no actual bug in the current code, because it uses the
lists in such a way as to initialize 'tqh_last' before any dereference.

Signed-off-by: Richard Cochran <richardcochran@gmail.com>

msg.c

@@ -42,7 +42,7 @@ struct message_storage {
 	struct ptp_message msg;
 } PACKED;
 
-static TAILQ_HEAD(msg_pool, ptp_message) msg_pool;
+static TAILQ_HEAD(msg_pool, ptp_message) msg_pool = TAILQ_HEAD_INITIALIZER(msg_pool);
 
 static struct {
 	int total;

port.c

@@ -376,6 +376,7 @@ static int add_foreign_master(struct port *p, struct ptp_message *m)
 			return 0;
 		}
 		memset(fc, 0, sizeof(*fc));
+		TAILQ_INIT(&fc->messages);
 		LIST_INSERT_HEAD(&p->foreign_masters, fc, list);
 		fc->port = p;
 		fc->dataset.sender = m->header.sourcePortIdentity;