Index: libxml2-2.11.6/python/libxml.c
===================================================================
--- libxml2-2.11.6.orig/python/libxml.c
+++ libxml2-2.11.6/python/libxml.c
@@ -266,7 +266,9 @@ xmlPythonFileReadRaw (void * context, ch
 #endif
     file = (PyObject *) context;
     if (file == NULL) return(-1);
-    ret = PyObject_CallMethod(file, (char *) "read", (char *) "(i)", len);
+    /* When read() returns a string, the length is in characters not bytes, so
+       request at most len / 4 characters to leave space for UTF-8 encoding. */
+    ret = PyObject_CallMethod(file, (char *) "read", (char *) "(i)", len / 4);
     if (ret == NULL) {
 	printf("xmlPythonFileReadRaw: result is NULL\n");
 	return(-1);
@@ -301,10 +303,12 @@ xmlPythonFileReadRaw (void * context, ch
 	Py_DECREF(ret);
 	return(-1);
     }
-    if (lenread > len)
-	memcpy(buffer, data, len);
-    else
-	memcpy(buffer, data, lenread);
+    if (lenread < 0 || lenread > len) {
+	printf("xmlPythonFileReadRaw: invalid lenread\n");
+	Py_DECREF(ret);
+	return(-1);
+    }
+    memcpy(buffer, data, lenread);
     Py_DECREF(ret);
     return(lenread);
 }
@@ -331,7 +335,9 @@ xmlPythonFileRead (void * context, char
 #endif
     file = (PyObject *) context;
     if (file == NULL) return(-1);
-    ret = PyObject_CallMethod(file, (char *) "io_read", (char *) "(i)", len);
+    /* When io_read() returns a string, the length is in characters not bytes, so
+       request at most len / 4 characters to leave space for UTF-8 encoding. */
+    ret = PyObject_CallMethod(file, (char *) "io_read", (char *) "(i)", len / 4);
     if (ret == NULL) {
 	printf("xmlPythonFileRead: result is NULL\n");
 	return(-1);
@@ -366,10 +372,12 @@ xmlPythonFileRead (void * context, char
 	Py_DECREF(ret);
 	return(-1);
     }
-    if (lenread > len)
-	memcpy(buffer, data, len);
-    else
-	memcpy(buffer, data, lenread);
+    if (lenread < 0 || lenread > len) {
+	printf("xmlPythonFileRead: invalid lenread\n");
+	Py_DECREF(ret);
+	return(-1);
+    }
+    memcpy(buffer, data, lenread);
     Py_DECREF(ret);
     return(lenread);
 }