issue2858: Fix potential memory corruption when bsddb.db.DBEnv.lock_get

and other bsddb.db object constructors raised an exception.
Debugging & patch by Neal Norowitz.

Lib/bsddb/test/test_lock.py

@@ -97,11 +97,7 @@ class LockingTestCase(unittest.TestCase):
         for t in threads:
             t.join()
 
-    def _DISABLED_test03_lock_timeout(self):
-        # Disabled as this test crashes the python interpreter built in
-        # debug mode with:
-        #  Fatal Python error: UNREF invalid object
-        # the error occurs as marked below.
+    def test03_lock_timeout(self):
         self.env.set_timeout(0, db.DB_SET_LOCK_TIMEOUT)
         self.env.set_timeout(0, db.DB_SET_TXN_TIMEOUT)
         self.env.set_timeout(123456, db.DB_SET_LOCK_TIMEOUT)
@@ -128,8 +124,6 @@ class LockingTestCase(unittest.TestCase):
         self.assertNotEqual(anID, anID2)
         lock = self.env.lock_get(anID, "shared lock", db.DB_LOCK_WRITE)
         start_time=time.time()
-        # FIXME: I see the UNREF crash as the interpreter trys to exit
-        # from this call to lock_get.
         self.assertRaises(db.DBLockNotGrantedError,
                 self.env.lock_get,anID2, "shared lock", db.DB_LOCK_READ)
         end_time=time.time()

Misc/NEWS

@@ -36,6 +36,9 @@ Extension Modules
 
 - bsddb module updated to version 4.6.4.
 
+- issue2858: Fix potential memory corruption when bsddb.db.DBEnv.lock_get
+  and other bsddb.db object constructors raised an exception.
+
 - Fixed #2870: cmathmodule.c compile error
 
 Library

Modules/_bsddb.c

@@ -903,7 +903,7 @@ newDBObject(DBEnvObject* arg, int flags)
             Py_DECREF(self->myenvobj);
             self->myenvobj = NULL;
         }
-        PyObject_Del(self);
+        Py_DECREF(self);
         self = NULL;
     }
     return self;
@@ -1010,7 +1010,7 @@ newDBEnvObject(int flags)
     err = db_env_create(&self->db_env, flags);
     MYDB_END_ALLOW_THREADS;
     if (makeDBError(err)) {
-        PyObject_Del(self);
+        Py_DECREF(self);
         self = NULL;
     }
     else {
@@ -1050,20 +1050,27 @@ static DBTxnObject*
 newDBTxnObject(DBEnvObject* myenv, DBTxnObject *parent, DB_TXN *txn, int flags)
 {
     int err;
-    DB_TXN *parent_txn=NULL;
+    DB_TXN *parent_txn = NULL;
 
     DBTxnObject* self = PyObject_New(DBTxnObject, &DBTxn_Type);
     if (self == NULL)
         return NULL;
 
     self->in_weakreflist = NULL;
+    self->children_txns = NULL;
+    self->children_dbs = NULL;
+    self->children_cursors = NULL;
+    self->children_sequences = NULL;
+    self->flag_prepare = 0;
+    self->parent_txn = NULL;
+    self->env = NULL;
 
     if (parent && ((PyObject *)parent!=Py_None)) {
-        parent_txn=parent->txn;
+        parent_txn = parent->txn;
     }
 
     if (txn) {
-        self->txn=txn;
+        self->txn = txn;
     } else {
         MYDB_BEGIN_ALLOW_THREADS;
 #if (DBVER >= 40)
@@ -1074,29 +1081,24 @@ newDBTxnObject(DBEnvObject* myenv, DBTxnObject *parent, DB_TXN *txn, int flags)
         MYDB_END_ALLOW_THREADS;
 
         if (makeDBError(err)) {
-            PyObject_Del(self);
+            Py_DECREF(self);
             return NULL;
         }
     }
 
-    if (parent_txn) { /* Can't use 'parent' because could be 'parent==Py_None' */
-        self->parent_txn=parent;
+    /* Can't use 'parent' because could be 'parent==Py_None' */
+    if (parent_txn) {
+        self->parent_txn = parent;
         Py_INCREF(parent);
         self->env = NULL;
-        INSERT_IN_DOUBLE_LINKED_LIST(parent->children_txns,self);
+        INSERT_IN_DOUBLE_LINKED_LIST(parent->children_txns, self);
     } else {
-        self->parent_txn=NULL;
+        self->parent_txn = NULL;
         Py_INCREF(myenv);
         self->env = myenv;
-        INSERT_IN_DOUBLE_LINKED_LIST(myenv->children_txns,self);
+        INSERT_IN_DOUBLE_LINKED_LIST(myenv->children_txns, self);
     }
 
-    self->children_txns=NULL;
-    self->children_dbs=NULL;
-    self->children_cursors=NULL;
-    self->children_sequences=NULL;
-    self->flag_prepare=0;
-
     return self;
 }
 
@@ -1151,7 +1153,7 @@ newDBLockObject(DBEnvObject* myenv, u_int32_t locker, DBT* obj,
 #endif
     MYDB_END_ALLOW_THREADS;
     if (makeDBError(err)) {
-        PyObject_Del(self);
+        Py_DECREF(self);
         self = NULL;
     }
 
@@ -1183,7 +1185,7 @@ newDBSequenceObject(DBObject* mydb,  int flags)
     self->mydb = mydb;
 
     INSERT_IN_DOUBLE_LINKED_LIST(self->mydb->children_sequences,self);
-    self->txn=NULL;
+    self->txn = NULL;
 
     self->in_weakreflist = NULL;
 
@@ -1191,8 +1193,7 @@ newDBSequenceObject(DBObject* mydb,  int flags)
     err = db_sequence_create(&self->sequence, self->mydb->db, flags);
     MYDB_END_ALLOW_THREADS;
     if (makeDBError(err)) {
-        Py_DECREF(self->mydb);
-        PyObject_Del(self);
+        Py_DECREF(self);
         self = NULL;
     }