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bpo-31728: Prevent crashes in _elementtree due to unsafe cleanup of Element.text and Element.tail (#3924)

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Oren Milman 2017-10-10 23:26:24 +03:00 • committed by Serhiy Storchaka
parent 93c5a5df8e
commit 39ecb9c71b
3 changed files with 62 additions and 34 deletions
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62
Modules/_elementtree.c
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@ -61,15 +61,22 @@ do { memory -= size; printf("%8d - %s\n", memory, comment); } while (0)
#define JOIN_SET(p, flag) ((void*) ((uintptr_t) (JOIN_OBJ(p)) | (flag)))
#define JOIN_OBJ(p) ((PyObject*) ((uintptr_t) (p) & ~(uintptr_t)1))
/* Py_SETREF for a PyObject* that uses a join flag. */
Py_LOCAL_INLINE(void)
_set_joined_ptr(PyObject **p, PyObject *new_joined_ptr)
{
PyObject *tmp = JOIN_OBJ(*p);
*p = new_joined_ptr;
Py_DECREF(tmp);
}
/* Py_CLEAR for a PyObject* that uses a join flag. Pass the pointer by
* reference since this function sets it to NULL.
*/
static void _clear_joined_ptr(PyObject **p)
{
if (*p) {
PyObject *tmp = JOIN_OBJ(*p);
*p = NULL;
Py_DECREF(tmp);
_set_joined_ptr(p, NULL);
}
}
@ -356,7 +363,6 @@ static int
element_init(PyObject *self, PyObject *args, PyObject *kwds)
{
PyObject *tag;
PyObject *tmp;
PyObject *attrib = NULL;
ElementObject *self_elem;
@ -397,15 +403,11 @@ element_init(PyObject *self, PyObject *args, PyObject *kwds)
Py_INCREF(tag);
Py_XSETREF(self_elem->tag, tag);
tmp = self_elem->text;
Py_INCREF(Py_None);
self_elem->text = Py_None;
Py_DECREF(JOIN_OBJ(tmp));
_set_joined_ptr(&self_elem->text, Py_None);
tmp = self_elem->tail;
Py_INCREF(Py_None);
self_elem->tail = Py_None;
Py_DECREF(JOIN_OBJ(tmp));
_set_joined_ptr(&self_elem->tail, Py_None);
return 0;
}
@ -675,12 +677,10 @@ _elementtree_Element_clear_impl(ElementObject *self)
dealloc_extra(self);
Py_INCREF(Py_None);
Py_DECREF(JOIN_OBJ(self->text));
self->text = Py_None;
_set_joined_ptr(&self->text, Py_None);
Py_INCREF(Py_None);
Py_DECREF(JOIN_OBJ(self->tail));
self->tail = Py_None;
_set_joined_ptr(&self->tail, Py_None);
Py_RETURN_NONE;
}
@ -702,13 +702,11 @@ _elementtree_Element___copy___impl(ElementObject *self)
if (!element)
return NULL;
Py_DECREF(JOIN_OBJ(element->text));
element->text = self->text;
Py_INCREF(JOIN_OBJ(element->text));
Py_INCREF(JOIN_OBJ(self->text));
_set_joined_ptr(&element->text, self->text);
Py_DECREF(JOIN_OBJ(element->tail));
element->tail = self->tail;
Py_INCREF(JOIN_OBJ(element->tail));
Py_INCREF(JOIN_OBJ(self->tail));
_set_joined_ptr(&element->tail, self->tail);
if (self->extra) {
if (element_resize(element, self->extra->length) < 0) {
@ -776,14 +774,12 @@ _elementtree_Element___deepcopy___impl(ElementObject *self, PyObject *memo)
text = deepcopy(JOIN_OBJ(self->text), memo);
if (!text)
goto error;
Py_DECREF(element->text);
element->text = JOIN_SET(text, JOIN_GET(self->text));
_set_joined_ptr(&element->text, JOIN_SET(text, JOIN_GET(self->text)));
tail = deepcopy(JOIN_OBJ(self->tail), memo);
if (!tail)
goto error;
Py_DECREF(element->tail);
element->tail = JOIN_SET(tail, JOIN_GET(self->tail));
_set_joined_ptr(&element->tail, JOIN_SET(tail, JOIN_GET(self->tail)));
if (self->extra) {
if (element_resize(element, self->extra->length) < 0)
@ -968,13 +964,13 @@ element_setstate_from_attributes(ElementObject *self,
Py_INCREF(tag);
Py_XSETREF(self->tag, tag);
_clear_joined_ptr(&self->text);
self->text = text ? JOIN_SET(text, PyList_CheckExact(text)) : Py_None;
Py_INCREF(JOIN_OBJ(self->text));
text = text ? JOIN_SET(text, PyList_CheckExact(text)) : Py_None;
Py_INCREF(JOIN_OBJ(text));
_set_joined_ptr(&self->text, text);
_clear_joined_ptr(&self->tail);
self->tail = tail ? JOIN_SET(tail, PyList_CheckExact(tail)) : Py_None;
Py_INCREF(JOIN_OBJ(self->tail));
tail = tail ? JOIN_SET(tail, PyList_CheckExact(tail)) : Py_None;
Py_INCREF(JOIN_OBJ(tail));
_set_joined_ptr(&self->tail, tail);
/* Handle ATTRIB and CHILDREN. */
if (!children && !attrib)
@ -2009,8 +2005,7 @@ element_text_setter(ElementObject *self, PyObject *value, void *closure)
{
_VALIDATE_ATTR_VALUE(value);
Py_INCREF(value);
Py_DECREF(JOIN_OBJ(self->text));
self->text = value;
_set_joined_ptr(&self->text, value);
return 0;
}
@ -2019,8 +2014,7 @@ element_tail_setter(ElementObject *self, PyObject *value, void *closure)
{
_VALIDATE_ATTR_VALUE(value);
Py_INCREF(value);
Py_DECREF(JOIN_OBJ(self->tail));
self->tail = value;
_set_joined_ptr(&self->tail, value);
return 0;
}