Memory leak when using handlers in multiple phases at same time.

• Key: MODPYTHON-181
• Type: Bug
• Status: Closed
• Resolution: Fixed
• Priority: Major
• Assignee: Graham Dumpleton
• Reporter: Graham Dumpleton
• Component/s: core
• Affects Version/s: 3.1.4, 3.3.x, 3.2.8
• Fix Version/s: 3.3.1

Description

When using handlers against multiple phases, ie.,

# .htaccess

PythonFixupHandler handlers
AddHandler mod_python .py
PythonHandler handlers

# handlers.py

from mod_python import apache

def handler(req):
  req.content_type = 'text/plain'
  req.write('handler')
  return apache.OK

def fixuphandler(req):
  return apache.OK

mod_python will leak memory on each request, which Apache child process sizes blowing out quite quickly.

The problem code is in python_handler() in 'src/mod_python.c'. Specifically the code does:

    if (!hle) {
        /* create a handler list object from dynamically registered handlers */
        request_obj->hlo = (hlistobject *)MpHList_FromHLEntry(dynhle, 1);
    }
    else {
        /* create a handler list object */
        request_obj->hlo = (hlistobject *)MpHList_FromHLEntry(hle, 1);

        /* add dynamically registered handlers, if any */
        if (dynhle) {
            MpHList_Append(request_obj->hlo, dynhle);
        }
    }

Problem is that request_obj->hlo can already be set by a prior phase's handler and by simply assigning to request_obj->hlo you get a memory leak as it refers to an existing Python object and it isn't being decref'd.

Thus, before this 'if' statement, it would appear that the following should
be inserted.

    if (request_obj->hlo)
        Py_DECREF(request_obj->hlo);

or:

    Py_XDECREF(request_obj->hlo);

Comments

[Graham Dumpleton]

Note that you will not actually see this change in the trunk now as changes related to MODPYTHON-155 have eliminated it, with the same handler list object now being kept for the whole life of the request and simply reused.