8000 [3.13] gh-126105: Fix crash in `ast` module, when `._fields` is delet… · python/cpython@265bc19 · GitHub
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[3.13] gh-126105: Fix crash in ast module, when ._fields is deleted (GH-126115) (#126130)
gh-126105: Fix crash in `ast` module, when `._fields` is deleted (GH-126115) Previously, if the `ast.AST._fields` attribute was deleted, attempts to create a new `as`t node would crash due to the assumption that `_fields` always had a non-NULL value. Now it has been fixed by adding an extra check to ensure that `_fields` does not have a NULL value (this can happen when you manually remove `_fields` attribute). (cherry picked from commit b2eaa75) Co-authored-by: sobolevn <mail@sobolevn.me>
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‎Lib/test/test_ast/test_ast.py‎

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Original file line numberDiff line numberDiff line change
@@ -72,6 +72,23 @@ def test_AST_objects(self):
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# "ast.AST constructor takes 0 positional arguments"
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ast.AST(2)
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def test_AST_fields_NULL_check(self):
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# See: https://github.com/python/cpython/issues/126105
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old_value = ast.AST._fields
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def cleanup():
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ast.AST._fields = old_value
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self.addCleanup(cleanup)
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del ast.AST._fields
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msg = "type object 'ast.AST' has no attribute '_fields'"
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# Both examples used to crash:
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with self.assertRaisesRegex(AttributeError, msg):
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ast.AST(arg1=123)
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with self.assertRaisesRegex(AttributeError, msg):
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ast.AST()
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def test_AST_garbage_collection(self):
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class X:
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pass

‎Misc/NEWS.d/next/Library/2024-10-29-11-45-44.gh-issue-126105.cOL-R6.rst‎

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@@ -0,0 +1 @@
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Fix a crash in :mod:`ast` when the :attr:`ast.AST._fields` attribute is deleted.

‎Parser/asdl_c.py‎

Lines changed: 8 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -881,19 +881,17 @@ def visitModule(self, mod):
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Py_ssize_t i, numfields = 0;
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int res = -1;
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PyObject *key, *value, *fields, *attributes = NULL, *remaining_fields = NULL;
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if (PyObject_GetOptionalAttr((PyObject*)Py_TYPE(self), state->_fields, &fields) < 0) {
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fields = PyObject_GetAttr((PyObject*)Py_TYPE(self), state->_fields);
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if (fields == NULL) {
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goto cleanup;
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}
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if (fields) {
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numfields = PySequence_Size(fields);
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if (numfields == -1) {
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goto cleanup;
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}
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remaining_fields = PySet_New(fields);
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}
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else {
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remaining_fields = PySet_New(NULL);
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numfields = PySequence_Size(fields);
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if (numfields == -1) {
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goto cleanup;
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}
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remaining_fields = PySet_New(fields);
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if (remaining_fields == NULL) {
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goto cleanup;
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}

‎Python/Python-ast.c‎

Lines changed: 8 additions & 10 deletions
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