bpo-44304: Fix crash in the sqlite3 module when the GC clears Statement objects

Author: pablogsal

Lib/sqlite3/test/userfunctions.py

@@ -23,6 +23,7 @@
 
 import unittest
 import unittest.mock
+import gc
 import sqlite3 as sqlite
 
 def func_returntext():
@@ -322,6 +323,22 @@ def test_func_deterministic_keyword_only(self):
  with self.assertRaises(TypeError):
  self.con.create_function("deterministic", 0, int, True)
 
+ def test_function_destructor_via_gc(self):
+ # See bpo-44304: The destructor of the user function can
+ # crash if is called without the GIL from the gc functions
+ dest = sqlite.connect(':memory:')
+ def md5sum(t):
+ return
+
+ dest.create_function("md5", 1, md5sum)
+ x = dest("create table lang (name, first_appeared)")
+ del md5sum, dest
+
+ y = [x]
+ y.append(y)
+
+ del x,y
+ gc.collect()
 
 class AggregateTests(unittest.TestCase):
  def setUp(self):

Misc/NEWS.d/next/Core and Builtins/2021-06-05-02-34-57.bpo-44304._MAoPc.rst

@@ -0,0 +1,2 @@
+Fix a crash in the :mod:`sqlite3` module that happened when the garbage
+collector clears :class:`sqlite.Statement` objects. Patch by Pablo Galindo

Modules/_sqlite/statement.c

@@ -403,6 +403,10 @@ stmt_dealloc(pysqlite_Statement *self)
  if (self->in_weakreflist != NULL) {
  PyObject_ClearWeakRefs((PyObject*)self);
  }
+ if (self->st) {
+ sqlite3_finalize(self->st);
+ self->st = 0;
+ }
  tp->tp_clear((PyObject *)self);
  tp->tp_free(self);
  Py_DECREF(tp);
@@ -411,13 +415,6 @@ stmt_dealloc(pysqlite_Statement *self)
 static int
 stmt_clear(pysqlite_Statement *self)
 {
- if (self->st) {
- Py_BEGIN_ALLOW_THREADS
- sqlite3_finalize(self->st);
- Py_END_ALLOW_THREADS
- self->st = 0;
- }
-
  Py_CLEAR(self->sql);
  return 0;
 }