audit: get rid of *NO* daemon at audit_pid=0 message

kauditd_send_skb is called after audit_pid was checked to be non-zero.

However, it can be set to 0 due to auditd exiting while kauditd_send_skb
is still executed and this can result in a spurious warning about missing
auditd.

Re-check audit_pid before printing the message.
Signed-off-by: Mateusz Guzik <mguzik@redhat.com>
Cc: Eric Paris <eparis@redhat.com>
Cc: linux-kernel@vger.kernel.org
Acked-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Eric Paris <eparis@redhat.com>

kernel/audit.c

@@ -410,10 +410,12 @@ static void kauditd_send_skb(struct sk_buff *skb)
 	err = netlink_unicast(audit_sock, skb, audit_nlk_portid, 0);
 	if (err < 0) {
 		BUG_ON(err != -ECONNREFUSED); /* Shouldn't happen */
-		printk(KERN_ERR "audit: *NO* daemon at audit_pid=%d\n", audit_pid);
-		audit_log_lost("auditd disappeared\n");
-		audit_pid = 0;
-		audit_sock = NULL;
+		if (audit_pid) {
+			printk(KERN_ERR "audit: *NO* daemon at audit_pid=%d\n", audit_pid);
+			audit_log_lost("auditd disappeared\n");
+			audit_pid = 0;
+			audit_sock = NULL;
+		}
 		/* we might get lucky and get this in the next auditd */
 		audit_hold_skb(skb);
 	} else