net: rds: drop VLA in rds_for_each_conn_info()

Avoid VLA[1] by using an already allocated buffer passed
by the caller.

[1] https://lkml.org/lkml/2018/3/7/621

Signed-off-by: Salvatore Mesoraca <s.mesoraca16@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/rds/connection.c

@@ -540,9 +540,9 @@ void rds_for_each_conn_info(struct socket *sock, unsigned int len,
 			  struct rds_info_iterator *iter,
 			  struct rds_info_lengths *lens,
 			  int (*visitor)(struct rds_connection *, void *),
+			  u64 *buffer,
 			  size_t item_len)
 {
-	uint64_t buffer[(item_len + 7) / 8];
 	struct hlist_head *head;
 	struct rds_connection *conn;
 	size_t i;