Graham Dumpleton wrote:
Graham Dumpleton wrote ..
Returning back up to _conn_read() in mod_python source code, we have
where core_input_filter() was called ap_get_brigade():
Py_BEGIN_ALLOW_THREADS;
rc = ap_get_brigade(c->input_filters, bb, mode, APR_BLOCK_READ, bufsize);
Py_END_ALLOW_THREADS;
if (! APR_STATUS_IS_SUCCESS(rc)) {
PyErr_SetObject(PyExc_IOError,
PyString_FromString("Connection read error"));
return NULL;
}
Since APR_SUCCESS was returned and assigned to "rc", no problem is detected.
The code which follows then assumes that the first bucket in the bucket
brigade actually contains valid data, when in fact the first bucket is
actually
crap as nothing was done to set up a valid bucket since EAGAIN was returned.
As a consequence it crashes.
Thus in summary, _conn_read() doesn't cater in any way for the possibility
that the initial socket read may have failed because of EAGAIN and thus
the bucket is bogus. The problem is, how is it mean't to know this if the
value APR_SUCCESS is returned by ap_get_brigade().
Extending the above code as:
Py_BEGIN_ALLOW_THREADS;
rc = ap_get_brigade(c->input_filters, bb, mode, APR_BLOCK_READ, bufsize);
Py_END_ALLOW_THREADS;
if (! APR_STATUS_IS_SUCCESS(rc)) {
PyErr_SetObject(PyExc_IOError,
PyString_FromString("Connection read error"));
return NULL;
}
/* Return empty string if no buckets. Can be caused by EAGAIN. */
if (APR_BRIGADE_EMPTY(bb)) {
return PyString_FromString("");
}
seems to fix the problem. Ie., use call to APR_BRIGADE_EMPTY(bb) to check
whether any new buckets added and returning empty string if not.
Can someone else seeing this issue try this fix and see if the tests then
work.
Note that APR_STATUS_IS_SUCCESS has been removed from apr 1.x, which is
one of the issues in getting mod_python to run in Apache 2.2. It looks
like we should just check if rc != 0. This is according to discussion
here featuring Greg Stein and Ryan Bloom:
http://www.mail-archive.com/dev@httpd.apache.org/msg21757.html
I'll update MODPYTHON-78 regarding Apache 2.2 with details on this and
apr_sockaddr_port_get which has also been removed in apr 1.x.
Jim
