ipv4: netfilter: arp_tables: fix information leak to userland

Structure arpt_getinfo is copied to userland with the field "name"
that has the last elements unitialized.  It leads to leaking of
contents of kernel stack memory.
Signed-off-by: Vasiliy Kulikov <segooon@gmail.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>

net/ipv4/netfilter/arp_tables.c

@@ -927,6 +927,7 @@ static int get_info(struct net *net, void __user *user,
 			private = &tmp;
 		}
 #endif
+		memset(&info, 0, sizeof(info));
 		info.valid_hooks = t->valid_hooks;
 		memcpy(info.hook_entry, private->hook_entry,
 		       sizeof(info.hook_entry));