[NETFILTER]: Fix logging regression

Loading one of the LOG target fails if a different target has already
registered itself as backend for the same family. This can affect the
ipt_LOG and ipt_ULOG modules when both are loaded.

Reported and tested by: <t.artem@mailcity.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/bridge/netfilter/ebt_log.c

@@ -196,10 +196,8 @@ static int __init ebt_log_init(void)
 	ret = ebt_register_watcher(&log);
 	if (ret < 0)
 		return ret;
-	ret = nf_log_register(PF_BRIDGE, &ebt_log_logger);
-	if (ret < 0 && ret != -EEXIST)
-		ebt_unregister_watcher(&log);
-	return ret;
+	nf_log_register(PF_BRIDGE, &ebt_log_logger);
+	return 0;
 }
 
 static void __exit ebt_log_fini(void)

net/bridge/netfilter/ebt_ulog.c

@@ -308,12 +308,8 @@ static int __init ebt_ulog_init(void)
 	else if ((ret = ebt_register_watcher(&ulog)))
 		sock_release(ebtulognl->sk_socket);
 
-	if (nf_log_register(PF_BRIDGE, &ebt_ulog_logger) < 0) {
-		printk(KERN_WARNING "ebt_ulog: not logging via ulog "
-		       "since somebody else already registered for PF_BRIDGE\n");
-		/* we cannot make module load fail here, since otherwise
-		 * ebtables userspace would abort */
-	}
+	if (ret == 0)
+		nf_log_register(PF_BRIDGE, &ebt_ulog_logger);
 
 	return ret;
 }

net/ipv4/netfilter/ipt_LOG.c

@@ -479,10 +479,8 @@ static int __init ipt_log_init(void)
 	ret = xt_register_target(&ipt_log_reg);
 	if (ret < 0)
 		return ret;
-	ret = nf_log_register(PF_INET, &ipt_log_logger);
-	if (ret < 0 && ret != -EEXIST)
-		xt_unregister_target(&ipt_log_reg);
-	return ret;
+	nf_log_register(PF_INET, &ipt_log_logger);
+	return 0;
 }
 
 static void __exit ipt_log_fini(void)

net/ipv6/netfilter/ip6t_LOG.c

@@ -493,10 +493,8 @@ static int __init ip6t_log_init(void)
 	ret = xt_register_target(&ip6t_log_reg);
 	if (ret < 0)
 		return ret;
-	ret = nf_log_register(PF_INET6, &ip6t_logger);
-	if (ret < 0 && ret != -EEXIST)
-		xt_unregister_target(&ip6t_log_reg);
-	return ret;
+	nf_log_register(PF_INET6, &ip6t_logger);
+	return 0;
 }
 
 static void __exit ip6t_log_fini(void)