[3.9] bpo-31746: Prevent segfaults when sqlite3.Connection is uninitialised (GH-27431) (GH-27465)

(cherry picked from commit 7e311e496b0e26b3d3c62fe9b0ed2a4677c37ee9)

Co-authored-by: Erlend Egeberg Aasland <erlend.aasland@innova.no>

1 files changed, 22 insertions, 7 deletions

diff --git a/Modules/_sqlite/connection.c b/Modules/_sqlite/connection.c
index df4e946..1cf3148 100644
--- a/Modules/_sqlite/connection.c
+++ b/Modules/_sqlite/connection.c
@@ -102,8 +102,6 @@ int pysqlite_connection_init(pysqlite_Connection* self, PyObject* args, PyObject
 
     database = PyBytes_AsString(database_obj);
 
-    self->initialized = 1;
-
     self->begin_statement = NULL;
 
     Py_CLEAR(self->statement_cache);
@@ -149,7 +147,7 @@ int pysqlite_connection_init(pysqlite_Connection* self, PyObject* args, PyObject
         Py_INCREF(isolation_level);
     }
     Py_CLEAR(self->isolation_level);
-    if (pysqlite_connection_set_isolation_level(self, isolation_level, NULL) < 0) {
+    if (pysqlite_connection_set_isolation_level(self, isolation_level, NULL) != 0) {
         Py_DECREF(isolation_level);
         return -1;
     }
@@ -208,6 +206,8 @@ int pysqlite_connection_init(pysqlite_Connection* self, PyObject* args, PyObject
     self->ProgrammingError      = pysqlite_ProgrammingError;
     self->NotSupportedError     = pysqlite_NotSupportedError;
 
+    self->initialized = 1;
+
     return 0;
 }
 
@@ -339,6 +339,12 @@ PyObject* pysqlite_connection_close(pysqlite_Connection* self, PyObject* args)
         return NULL;
     }
 
+    if (!self->initialized) {
+        PyErr_SetString(pysqlite_ProgrammingError,
+                        "Base Connection.__init__ not called.");
+        return NULL;
+    }
+
     pysqlite_do_all_statements(self, ACTION_FINALIZE, 1);
 
     if (self->db) {
@@ -1143,6 +1149,9 @@ int pysqlite_check_thread(pysqlite_Connection* self)
 
 static PyObject* pysqlite_connection_get_isolation_level(pysqlite_Connection* self, void* unused)
 {
+    if (!pysqlite_check_connection(self)) {
+        return NULL;
+    }
     Py_INCREF(self->isolation_level);
     return self->isolation_level;
 }
@@ -1175,11 +1184,17 @@ pysqlite_connection_set_isolation_level(pysqlite_Connection* self, PyObject* iso
         return -1;
     }
     if (isolation_level == Py_None) {
-        PyObject *res = pysqlite_connection_commit(self, NULL);
-        if (!res) {
-            return -1;
+        /* We might get called during connection init, so we cannot use
+         * pysqlite_connection_commit() here. */
+        if (self->db && !sqlite3_get_autocommit(self->db)) {
+            int rc;
+            Py_BEGIN_ALLOW_THREADS
+            rc = sqlite3_exec(self->db, "COMMIT", NULL, NULL, NULL);
+            Py_END_ALLOW_THREADS
+            if (rc != SQLITE_OK) {
+                return _pysqlite_seterror(self->db, NULL);
+            }
         }
-        Py_DECREF(res);
 
         self->begin_statement = NULL;
     } else {