netfilter: nf_log regression fix

commit ca735b3aaa945626ba65a3e51145bfe4ecd9e222
'netfilter: use a linked list of loggers'
introduced an array of list_head in "struct nf_logger", but
forgot to initialize it in nf_log_register(). This resulted
in oops when calling nf_log_unregister() at module unload time.

Reported-and-tested-by: Mariusz Kozlowski <m.kozlowski@tuxland.pl>
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Acked-by: Eric Leblond <eric@inl.fr>
Signed-off-by: Patrick McHardy <kaber@trash.net>

net/netfilter/nf_log.c

@@ -36,10 +36,14 @@ static struct nf_logger *__find_logger(int pf, const char *str_logger)
 int nf_log_register(u_int8_t pf, struct nf_logger *logger)
 {
 	const struct nf_logger *llog;
+	int i;
 
 	if (pf >= ARRAY_SIZE(nf_loggers))
 		return -EINVAL;
 
+	for (i = 0; i < ARRAY_SIZE(logger->list); i++)
+		INIT_LIST_HEAD(&logger->list[i]);
+
 	mutex_lock(&nf_log_mutex);
 
 	if (pf == NFPROTO_UNSPEC) {