The virSecurityManagerGetPrivateData function in security/security_manager.c in libvirt 0.8.8 through 0.9.1 uses the wrong argument for a sizeof call, which causes incorrect processing of "security manager private data" that "reopens disk probing" and might allow guest OS users to read arbitrary files on the host OS.  NOTE: this vulnerability exists because of a CVE-2010-2238 regression.