bpo-36073: Raise ProgrammingError on recursive usage of cursors in sqlite converters

Lib/sqlite3/test/regression.py

@@ -415,9 +415,44 @@ def test_return_empty_bytestring(self):
         self.assertEqual(val, b'')
 
 
+class ConverterProgrammingErrorTestCase(unittest.TestCase):
+    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)')
+
+        sqlite.converters['CURSOR_INIT'] = lambda x: self.cur.__init__(self.con)
+        sqlite.converters['CURSOR_CLOSE'] = lambda x: self.cur.close()
+        sqlite.converters['CURSOR_ITER'] = lambda x, l=[]: self.cur.fetchone() if l else l.append(None)
+
+    def tearDown(self):
+        del sqlite.converters['CURSOR_INIT']
+        del sqlite.converters['CURSOR_CLOSE']
+        del sqlite.converters['CURSOR_ITER']
+        self.cur.close()
+        self.con.close()
+
+    def test_cursor_init(self):
+        self.cur.execute('insert into test(x) values (?)', ('foo',))
+        with self.assertRaises(sqlite.ProgrammingError):
+            self.cur.execute('select x as "x [CURSOR_INIT]", x from test')
+
+    def test_cursor_close(self):
+        self.cur.execute('insert into test(x) values (?)', ('foo',))
+        with self.assertRaises(sqlite.ProgrammingError):
+            self.cur.execute('select x as "x [CURSOR_CLOSE]", x from test')
+
+    def test_cursor_iter(self):
+        self.cur.executemany('insert into test(x) values (?)', (('foo',),) * 2)
+        self.cur.execute('select x as "x [CURSOR_ITER]", x from test')
+        with self.assertRaises(sqlite.ProgrammingError):
+            self.cur.fetchone()
+
+
 def suite():
     tests = [
-        RegressionTests
+        RegressionTests,
+        ConverterProgrammingErrorTestCase,
     ]
     return unittest.TestSuite(
         [unittest.TestLoader().loadTestsFromTestCase(t) for t in tests]

Misc/NEWS.d/next/Library/2019-06-22-11-01-45.bpo-36073.ED8mB9.rst

@@ -0,0 +1,2 @@
+Raise :exc:`~sqlite3.ProgrammingError` on recursive usage of cursors in
+:mod:`sqlite3` converters. Patch by Sergey Fedoseev.

Modules/_sqlite/cursor.c

@@ -26,6 +26,19 @@
 #include "util.h"
 #include "clinic/cursor.c.h"
 
+static int
+check_cursor_locked(pysqlite_Cursor* cur)
+{
+    if (cur->locked) {
+        PyErr_SetString(
+            pysqlite_ProgrammingError,
+            "Recursive use of cursors not allowed."
+        );
+        return 0;
+    }
+    return 1;
+}
+
 /*[clinic input]
 module _sqlite3
 class _sqlite3.Cursor "pysqlite_Cursor *" "pysqlite_CursorType"
@@ -47,6 +60,10 @@ pysqlite_cursor_init_impl(pysqlite_Cursor *self,
                           pysqlite_Connection *connection)
 /*[clinic end generated code: output=ac59dce49a809ca8 input=a8a4f75ac90999b2]*/
 {
+    if (!check_cursor_locked(self)) {
+        return -1;
+    }
+
     Py_INCREF(connection);
     Py_XSETREF(self->connection, connection);
     Py_CLEAR(self->statement);
@@ -384,12 +401,9 @@ static int check_cursor(pysqlite_Cursor* cur)
         return 0;
     }
 
-    if (cur->locked) {
-        PyErr_SetString(pysqlite_ProgrammingError, "Recursive use of cursors not allowed.");
-        return 0;
-    }
-
-    return pysqlite_check_thread(cur->connection) && pysqlite_check_connection(cur->connection);
+    return check_cursor_locked(cur) &&
+        pysqlite_check_thread(cur->connection) &&
+        pysqlite_check_connection(cur->connection);
 }
 
 static PyObject *
@@ -811,7 +825,9 @@ pysqlite_cursor_iternext(pysqlite_Cursor *self)
         }
 
         if (rc == SQLITE_ROW) {
+            self->locked = 1;
             self->next_row = _pysqlite_fetch_one_row(self);
+            self->locked = 0;
             if (self->next_row == NULL) {
                 (void)pysqlite_statement_reset(self->statement);
                 return NULL;
@@ -962,6 +978,10 @@ static PyObject *
 pysqlite_cursor_close_impl(pysqlite_Cursor *self)
 /*[clinic end generated code: output=b6055e4ec6fe63b6 input=08b36552dbb9a986]*/
 {
+    if (!check_cursor_locked(self)) {
+        return NULL;
+    }
+
     if (!self->connection) {
         PyErr_SetString(pysqlite_ProgrammingError,
                         "Base Cursor.__init__ not called.");