n3 It is thus clear that waste insofar as it involves protection for the security interest of mortgagees (Civ. Code, @ 2929) is limited to protection against harm committed by persons in possession of the property subject to the lien. However, it is equally clear that a mortgagee's security interest can be impaired by harm to the property committed by third persons not in possession and that a mortgagee can recover damages in tort for such impairment of his security interest. [Citations Omitted.] This recovery against third parties involves different considerations and rules because the person sued is not the debtor-mortgagor, who is afforded a variety of legislative and judicial protections [Citations Omitted.]