Fix refcounts after porting to GetItemRef & better error checking (#126)

src/_imaging.c

@@ -2251,6 +2251,11 @@ _getcolors(ImagingObject *self, PyObject *args) {
             ImagingColorItem *v = &items[i];
             PyObject *item = Py_BuildValue(
                 "iN", v->count, getpixel(self->image, self->access, v->x, v->y));
+            if (item == NULL) {
+                Py_DECREF(out);
+                free(items);
+                return NULL;
+            }
             PyList_SetItem(out, i, item);
         }
     }

src/_imagingft.c

@@ -1205,9 +1205,15 @@ font_getvarnames(FontObject *self) {
 
     num_namedstyles = master->num_namedstyles;
     list_names = PyList_New(num_namedstyles);
+    if (list_names == NULL) {
+        FT_Done_MM_Var(library, master);
+        return NULL;
+    }
 
     int *list_names_filled = PyMem_Malloc(num_namedstyles * sizeof(int));
     if (list_names_filled == NULL) {
+        Py_DECREF(list_names);
+        FT_Done_MM_Var(library, master);
         return PyErr_NoMemory();
     }
 
@@ -1215,15 +1221,11 @@ font_getvarnames(FontObject *self) {
         list_names_filled[i] = 0;
     }
 
-    if (list_names == NULL) {
-        FT_Done_MM_Var(library, master);
-        return NULL;
-    }
-
     name_count = FT_Get_Sfnt_Name_Count(self->face);
     for (i = 0; i < name_count; i++) {
         error = FT_Get_Sfnt_Name(self->face, i, &name);
         if (error) {
+            PyMem_Free(list_names_filled);
             Py_DECREF(list_names);
             FT_Done_MM_Var(library, master);
             return geterror(error);
@@ -1236,6 +1238,12 @@ font_getvarnames(FontObject *self) {
 
             if (master->namedstyle[j].strid == name.name_id) {
                 list_name = Py_BuildValue("y#", name.string, name.string_len);
+                if (list_name == NULL) {
+                    PyMem_Free(list_names_filled);
+                    Py_DECREF(list_names);
+                    FT_Done_MM_Var(library, master);
+                    return NULL;
+                }
                 PyList_SetItem(list_names, j, list_name);
                 list_names_filled[j] = 1;
                 break;
@@ -1301,9 +1309,15 @@ font_getvaraxes(FontObject *self) {
 
             if (name.name_id == axis.strid) {
                 axis_name = Py_BuildValue("y#", name.string, name.string_len);
+                if (axis_name == NULL) {
+                    Py_DECREF(list_axis);
+                    Py_DECREF(list_axes);
+                    FT_Done_MM_Var(library, master);
+                    return NULL;
+                }
                 PyDict_SetItemString(
                     list_axis, "name", axis_name ? axis_name : Py_None);
-                Py_XDECREF(axis_name);
+                Py_DECREF(axis_name);
                 break;
             }
         }
@@ -1357,7 +1371,12 @@ font_setvaraxes(FontObject *self, PyObject *args) {
         return PyErr_NoMemory();
     }
     for (i = 0; i < num_coords; i++) {
-        item = PyList_GET_ITEM(axes, i);
+        item = PyList_GetItemRef(axes, i);
+        if (item == NULL) {
+            free(coords);
+            return NULL;
+        }
+
         if (PyFloat_Check(item)) {
             coord = PyFloat_AS_DOUBLE(item);
         } else if (PyLong_Check(item)) {
@@ -1365,10 +1384,12 @@ font_setvaraxes(FontObject *self, PyObject *args) {
         } else if (PyNumber_Check(item)) {
             coord = PyFloat_AsDouble(item);
         } else {
+            Py_DECREF(item);
             free(coords);
             PyErr_SetString(PyExc_TypeError, "list must contain numbers");
             return NULL;
         }
+        Py_DECREF(item);
         coords[i] = coord * 65536;
     }
 

src/encode.c

@@ -673,10 +673,16 @@ PyImaging_LibTiffEncoderNew(PyObject *self, PyObject *args) {
         TRACE(("tags size: %d\n", (int)tags_size));
         for (pos = 0; pos < tags_size; pos++) {
             item = PyList_GetItemRef(tags, pos);
+            if (item == NULL) {
+                return NULL;
+            }
+
             if (!PyTuple_Check(item) || PyTuple_Size(item) != 2) {
+                Py_DECREF(item);
                 PyErr_SetString(PyExc_ValueError, "Invalid tags list");
                 return NULL;
             }
+            Py_DECREF(item);
         }
         pos = 0;
     }
@@ -705,10 +711,16 @@ PyImaging_LibTiffEncoderNew(PyObject *self, PyObject *args) {
     num_core_tags = sizeof(core_tags) / sizeof(int);
     for (pos = 0; pos < tags_size; pos++) {
         item = PyList_GetItemRef(tags, pos);
+        if (item == NULL) {
+            return NULL;
+        }
+
         // We already checked that tags is a 2-tuple list.
-        key = PyTuple_GetItem(item, 0);
+        key = PyTuple_GET_ITEM(item, 0);
         key_int = (int)PyLong_AsLong(key);
-        value = PyTuple_GetItem(item, 1);
+        value = PyTuple_GET_ITEM(item, 1);
+        Py_DECREF(item);
+
         status = 0;
         is_core_tag = 0;
         is_var_length = 0;

src/path.c

@@ -26,6 +26,7 @@
  */
 
 #include "Python.h"
+#include "thirdparty/pythoncapi_compat.h"
 #include "libImaging/Imaging.h"
 
 #include <math.h>
@@ -179,14 +180,21 @@ PyPath_Flatten(PyObject *data, double **pxy) {
         }                                                               \
         free(xy);                                                       \
         return -1;                                                      \
+    }                                                                   \
+    if (decref) {                                                       \
+        Py_DECREF(op);                                                  \
     }
 
     /* Copy table to path array */
     if (PyList_Check(data)) {
         for (i = 0; i < n; i++) {
             double x, y;
-            PyObject *op = PyList_GET_ITEM(data, i);
+            PyObject *op = PyList_GetItemRef(data, i);
-            assign_item_to_array(op, 0);
+            if (op == NULL) {
+                free(xy);
+                return -1;
+            }
+            assign_item_to_array(op, 1);
         }
     } else if (PyTuple_Check(data)) {
         for (i = 0; i < n; i++) {
@@ -209,7 +217,6 @@ PyPath_Flatten(PyObject *data, double **pxy) {
                 }
             }
             assign_item_to_array(op, 1);
-            Py_DECREF(op);
         }
     }