gh-80254: Disallow recursive usage of cursors in `sqlite3` converters (#29054)

Co-authored-by: Sergey Fedoseev <fedoseev.sergey@gmail.com>
Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>

1 files changed, 39 insertions, 0 deletions

diff --git a/Lib/test/test_sqlite3/test_regression.py b/Lib/test/test_sqlite3/test_regression.py
index aebea59..19bb84b 100644
--- a/Lib/test/test_sqlite3/test_regression.py
+++ b/Lib/test/test_sqlite3/test_regression.py
@@ -27,6 +27,7 @@ import weakref
 import functools
 
 from test import support
+from unittest.mock import patch
 from test.test_sqlite3.test_dbapi import memory_database, managed_connect, cx_limit
 
 
@@ -469,5 +470,43 @@ class RegressionTests(unittest.TestCase):
             self.assertEqual(steps, values)
 
 
+class RecursiveUseOfCursors(unittest.TestCase):
+    # GH-80254: sqlite3 should not segfault for recursive use of cursors.
+    msg = "Recursive use of cursors not allowed"
+
+    def setUp(self):
+        self.con = sqlite.connect(":memory:",
+                                  detect_types=sqlite.PARSE_COLNAMES)
+        self.cur = self.con.cursor()
+        self.cur.execute("create table test(x foo)")
+        self.cur.executemany("insert into test(x) values (?)",
+                             [("foo",), ("bar",)])
+
+    def tearDown(self):
+        self.cur.close()
+        self.con.close()
+
+    def test_recursive_cursor_init(self):
+        conv = lambda x: self.cur.__init__(self.con)
+        with patch.dict(sqlite.converters, {"INIT": conv}):
+            self.cur.execute(f'select x as "x [INIT]", x from test')
+            self.assertRaisesRegex(sqlite.ProgrammingError, self.msg,
+                                   self.cur.fetchall)
+
+    def test_recursive_cursor_close(self):
+        conv = lambda x: self.cur.close()
+        with patch.dict(sqlite.converters, {"CLOSE": conv}):
+            self.cur.execute(f'select x as "x [CLOSE]", x from test')
+            self.assertRaisesRegex(sqlite.ProgrammingError, self.msg,
+                                   self.cur.fetchall)
+
+    def test_recursive_cursor_iter(self):
+        conv = lambda x, l=[]: self.cur.fetchone() if l else l.append(None)
+        with patch.dict(sqlite.converters, {"ITER": conv}):
+            self.cur.execute(f'select x as "x [ITER]", x from test')
+            self.assertRaisesRegex(sqlite.ProgrammingError, self.msg,
+                                   self.cur.fetchall)
+
+
 if __name__ == "__main__":
     unittest.main()