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bpo-31455: avoid calling "PyObject_GetAttrString()" with a live exception set #3545

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Merged
serhiy-storchaka merged 5 commits into from
Sep 14, 2017
Merged

bpo-31455: avoid calling "PyObject_GetAttrString()" with a live exception set #3545

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a9a6875
Avoid calling "PyObject_GetAttrString()" (and potentially executing u…
Sep 13, 2017
e0b8790
Ignore only AttributeError on attribute lookups in ElementTree.XMLPar…
Sep 13, 2017
5253d56
Add News entry for bpo-31544
Sep 13, 2017
3e1c77b
Give test a more specific name and move it further down as it tests m…
Sep 14, 2017
8cb95c6
Fix C code style.
Sep 14, 2017
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23 changes: 23 additions & 0 deletions Lib/test/test_xml_etree.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2400,6 +2400,29 @@ def _check_sample1_element(self, e):
self.assertEqual(child.tail, 'tail')
self.assertEqual(child.attrib, {})

def test_exceptions(self):

@serhiy-storchaka serhiy-storchaka Sep 14, 2017

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Wouldn't XMLParserTest be better place? In any case I think it is better to place this method at the end of the class, after testing normal cases.

And maybe use more specific method name? "test_builder_attribute_errors" or something like.

@scoder scoder Sep 14, 2017

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Done. I kept it in the test class because the exceptions are related to the behaviour of the TreeBuilder.

class RaisingBuilder:
def __init__(self, raise_in=None, what=ValueError):
self.raise_in = raise_in
self.what = what

def __getattr__(self, name):
if name == self.raise_in:
raise self.what(self.raise_in)
def handle(*args):
pass
return handle

ET.XMLParser(target=RaisingBuilder())
# cET also checks for 'close' and 'doctype', PyET does it only at need
for event in ('start', 'data', 'end', 'comment', 'pi'):
with self.assertRaisesRegex(ValueError, event):
ET.XMLParser(target=RaisingBuilder(event))

ET.XMLParser(target=RaisingBuilder(what=AttributeError))
for event in ('start', 'data', 'end', 'comment', 'pi'):
ET.XMLParser(target=RaisingBuilder(event, what=AttributeError))

@serhiy-storchaka serhiy-storchaka Sep 14, 2017

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Close the parser explicitly. Just for the case.

@scoder scoder Sep 14, 2017

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Done. (Requires parsing something, though.)


def test_dummy_builder(self):
class BaseDummyBuilder:
def close(self):
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2017-09-13-19-55-35.bpo-31544.beTh6t.rst
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@@ -0,0 +1,2 @@
The C accelerator module of ElementTree ignored exceptions raised when
looking up TreeBuilder target methods in XMLParser().
27 changes: 25 additions & 2 deletions Modules/_elementtree.c
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Expand Up @@ -3259,6 +3259,17 @@ xmlparser_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
return (PyObject *)self;
}

static int
ignore_attribute_error(PyObject *value) {

@serhiy-storchaka serhiy-storchaka Sep 14, 2017

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Put this { on new line.

@scoder scoder Sep 14, 2017

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Done.

if (value == NULL) {
if (!PyErr_ExceptionMatches(PyExc_AttributeError)) {
return -1;
}
PyErr_Clear();
}
return 0;
}

/*[clinic input]
_elementtree.XMLParser.__init__

Expand Down Expand Up @@ -3313,14 +3324,26 @@ _elementtree_XMLParser___init___impl(XMLParserObject *self, PyObject *html,
self->target = target;

self->handle_start = PyObject_GetAttrString(target, "start");
if (ignore_attribute_error(self->handle_start))

@serhiy-storchaka serhiy-storchaka Sep 14, 2017

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New PEP 7 rules require braces even around simple if body.

@scoder scoder Sep 14, 2017

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Done. (Sad in this case, given the relation between "active" code and error handling code.)

return -1;
self->handle_data = PyObject_GetAttrString(target, "data");
if (ignore_attribute_error(self->handle_data))
return -1;
self->handle_end = PyObject_GetAttrString(target, "end");
if (ignore_attribute_error(self->handle_end))
return -1;
self->handle_comment = PyObject_GetAttrString(target, "comment");
if (ignore_attribute_error(self->handle_comment))
return -1;
self->handle_pi = PyObject_GetAttrString(target, "pi");
if (ignore_attribute_error(self->handle_pi))
return -1;
self->handle_close = PyObject_GetAttrString(target, "close");
if (ignore_attribute_error(self->handle_close))
return -1;
self->handle_doctype = PyObject_GetAttrString(target, "doctype");

PyErr_Clear();
if (ignore_attribute_error(self->handle_doctype))
return -1;

/* configure parser */
EXPAT(SetUserData)(self->parser, self);
Expand Down