Those problems occur without the patch. Feel free to correct me if I'm missing something, but AFAIK the only problem the patch introduces is not saving history when killed.

• In histcopy(), check the result of the input fopen and bail out before clobbering the output file.
  
• I don't agree that if the user doesn't have a ~/.ash_history, or have an empty one, or /tmp is full etc they should be locked out. Return instead of exit?
  
• The tmppath directory shouldn't be created with mode 0777 (predictable filenames in world-writable directories are a bit exploitable), 0700 will do.
  
• One could trigger a buffer overrun by feeding the shell a long $HOME (though that doesn't give any additional privileges). Using concat_path_file for tmppath would be safer than malloc/strncat here.