[AUDIT] Requeue messages at head of queue, up to audit_backlog

If netlink_unicast() fails, requeue the skb back at the head of the queue
it just came from, instead of the tail. And do so unless we've exceeded
the audit_backlog limit; not according to some other arbitrary limit.

From: Chris Wright <[e-mail]>
Signed-off-by: David Woodhouse <[e-mail]>

kernel/audit.c

···
 	int		     total;
 	int		     type;
 	int		     pid;
-	int		     count; /* Times requeued */
 };
 
 void audit_set_type(struct audit_buffer *ab, int type)
···
 			retval = netlink_unicast(audit_sock, skb, audit_pid,
 						 MSG_DONTWAIT);
 		}
-		if (retval == -EAGAIN && ab->count < 5) {
-			++ab->count;
-			skb_queue_tail(&ab->sklist, skb);
+		if (retval == -EAGAIN &&
+		    (atomic_read(&audit_backlog)) < audit_backlog_limit) {
+			skb_queue_head(&ab->sklist, skb);
 			audit_log_end_irq(ab);
 			return 1;
 		}
···
 	ab->total = 0;
 	ab->type  = AUDIT_KERNEL;
 	ab->pid   = 0;
-	ab->count = 0;
 
 #ifdef CONFIG_AUDITSYSCALL
 	if (ab->ctx)