python · serhiy-storchaka · Mar 2, 2017 · Mar 1, 2017 · Mar 2, 2017
diff --git a/Misc/NEWS b/Misc/NEWS
@@ -10,6 +10,9 @@ What's New in Python 3.6.1 release candidate 1?
 Core and Builtins
 -----------------

+- bpo-29683: Fixes to memory allocation in _PyCode_SetExtra.  Patch by
+  Brian Coleman.
+
 - bpo-29684: Fix minor regression of PyEval_CallObjectWithKeywords.
  It should raise TypeError when kwargs is not a dict.  But it might
  cause segv when args=NULL and kwargs is not a dict.

diff --git a/Objects/codeobject.c b/Objects/codeobject.c
@@ -856,16 +856,15 @@ _PyCode_SetExtra(PyObject *code, Py_ssize_t index, void *extra)
    _PyCodeObjectExtra *co_extra = (_PyCodeObjectExtra *) o->co_extra;

    if (co_extra == NULL) {
-        o->co_extra = (_PyCodeObjectExtra*) PyMem_Malloc(
-            sizeof(_PyCodeObjectExtra));
-        if (o->co_extra == NULL) {
+        co_extra = PyMem_Malloc(sizeof(_PyCodeObjectExtra));
+        if (co_extra == NULL) {
            return -1;
        }
-        co_extra = (_PyCodeObjectExtra *) o->co_extra;

        co_extra->ce_extras = PyMem_Malloc(
            tstate->co_extra_user_count * sizeof(void*));
        if (co_extra->ce_extras == NULL) {
+            PyMem_Free(co_extra);
            return -1;
        }

@@ -874,20 +873,25 @@ _PyCode_SetExtra(PyObject *code, Py_ssize_t index, void *extra)
        for (Py_ssize_t i = 0; i < co_extra->ce_size; i++) {
            co_extra->ce_extras[i] = NULL;
        }
+
+        o->co_extra = co_extra;
    }
    else if (co_extra->ce_size <= index) {
-        co_extra->ce_extras = PyMem_Realloc(
+        void** ce_extras = PyMem_Realloc(
            co_extra->ce_extras, tstate->co_extra_user_count * sizeof(void*));

-        if (co_extra->ce_extras == NULL) {
+        if (ce_extras == NULL) {
            return -1;
        }

-        co_extra->ce_size = tstate->co_extra_user_count;
-
-        for (Py_ssize_t i = co_extra->ce_size; i < co_extra->ce_size; i++) {
-            co_extra->ce_extras[i] = NULL;
+        for (Py_ssize_t i = co_extra->ce_size;
+             i < tstate->co_extra_user_count;
+             i++) {
+            ce_extras[i] = NULL;
        }
+
+        co_extra->ce_extras = ce_extras;
+        co_extra->ce_size = tstate->co_extra_user_count;
    }

    co_extra->ce_extras[index] = extra;