Ceph

The following code explains the situation quite well, I think:

void RGWAccessControlPolicy::xml_end(const char *el) {           
  acl = *(RGWAccessControlList *)find_first("AccessControlList");
  owner = *(ACLOwner *)find_first("Owner");
} 

We have no idea whether find_first will find either of these things, or return NULL!

If AccessControlList isn't found, of course, the XML is malformed. But that still should not cause us to segfault.

Unfortunately, expat is not a validating XML parser, so we can't just validate against a schema.