Reading dynamic objects from incomplete buffer enters infinite loop

[GoogleCodeExporter]

When attempting to decode a dynamic object from an incomplete buffer enters an 
infinite loop in the C decoder.

See attached source for example.

Original issue reported on code.google.com by chris.ta...@thesecondrow.com on 19 Apr 2012 at 10:36

Attachments:

• demo.py

[GoogleCodeExporter]

Changing Decoder_readPyString in context.c to:

   static PyObject* Decoder_readPyString(DecoderObj *self, int len)
   {
       if (self->int_buf) {
          return Buffer_readPyString((BufferObj*)self->buf, len); 
       }

       PyObject *tmp = self->_buf_str;
       PyObject *py_len = PyInt_FromLong((long)len);
       if (!py_len)
           return NULL;
       self->_buf_str = PyObject_CallMethodObjArgs(self->buf, self->read_name, py_len, NULL);

       int buf_len = PyString_Size(self->_buf_str);
       if (buf_len < len){
          char error_str[100];
          sprintf(error_str, "Attempted to read %d bytes. Received %d", len, buf_len);
          PyErr_SetString(amfast_ContextError, error_str);
          return NULL;
       }

       char *buf_str = PyString_AsString(self->_buf_str);

       Py_DECREF(py_len);
       Py_XDECREF(tmp); // Decrement reference to OLD string.
       return self->_buf_str;
   }

May fix the issue. I'm not familiar enough with the code to know about any 
side-effects this may cause.

Original comment by chris.ta...@thesecondrow.com on 19 Apr 2012 at 11:05

[GoogleCodeExporter]

thanks for the code submission.

What is the purpose of the following line?

char *buf_str = PyString_AsString(self->_buf_str);

Original comment by dthomp...@gmail.com on 21 Apr 2012 at 3:55

[GoogleCodeExporter]

Hi,

That line is probably an error, I'm not the most proficient c coder

Original comment by c.targ...@gmail.com on 21 Apr 2012 at 4:56

[GoogleCodeExporter]

I made a couple of changes to your code and pushed the change to trunk.

Original comment by dthomp...@gmail.com on 22 Apr 2012 at 9:54

• Changed state: Fixed