Your logo will likely contain many company assets like your brand/company name, your colour scheme and any mascots. Therefore it is unlikely that a logo designer could claim copyright. However, to be absolutely safe, you can simply upgrade your project with an IP Agreement, which is signed at the start of the project and ensures your rights and ownership of the completed work. You may also ask the freelancer to sign a Non Disclosure Agreement (NDA), which stipulates that the freelancer will not disclose the details of the project to anyone else.