Issue #7561: Operations on empty bytearrays (such as `int(bytearray())`)

could crash in many places because of the PyByteArray_AS_STRING() macro
returning NULL.  The macro now returns a statically allocated empty
string instead.

1 files changed, 6 insertions, 17 deletions

diff --git a/Objects/bytearrayobject.c b/Objects/bytearrayobject.c
index 308bd07..fdeec4c 100644
--- a/Objects/bytearrayobject.c
+++ b/Objects/bytearrayobject.c
@@ -5,23 +5,16 @@
 #include "structmember.h"
 #include "bytes_methods.h"
 
-static PyByteArrayObject *nullbytes = NULL;
+char _PyByteArray_empty_string[] = "";
 
 void
 PyByteArray_Fini(void)
 {
-    Py_CLEAR(nullbytes);
 }
 
 int
 PyByteArray_Init(void)
 {
-    nullbytes = PyObject_New(PyByteArrayObject, &PyByteArray_Type);
-    if (nullbytes == NULL)
-        return 0;
-    nullbytes->ob_bytes = NULL;
-    Py_SIZE(nullbytes) = nullbytes->ob_alloc = 0;
-    nullbytes->ob_exports = 0;
     return 1;
 }
 
@@ -74,7 +67,7 @@ bytearray_buffer_getreadbuf(PyByteArrayObject *self, Py_ssize_t index, const voi
                 "accessing non-existent bytes segment");
         return -1;
     }
-    *ptr = (void *)self->ob_bytes;
+    *ptr = (void *)PyByteArray_AS_STRING(self);
     return Py_SIZE(self);
 }
 
@@ -86,7 +79,7 @@ bytearray_buffer_getwritebuf(PyByteArrayObject *self, Py_ssize_t index, const vo
                 "accessing non-existent bytes segment");
         return -1;
     }
-    *ptr = (void *)self->ob_bytes;
+    *ptr = (void *)PyByteArray_AS_STRING(self);
     return Py_SIZE(self);
 }
 
@@ -106,7 +99,7 @@ bytearray_buffer_getcharbuf(PyByteArrayObject *self, Py_ssize_t index, const cha
                 "accessing non-existent bytes segment");
         return -1;
     }
-    *ptr = self->ob_bytes;
+    *ptr = PyByteArray_AS_STRING(self);
     return Py_SIZE(self);
 }
 
@@ -119,10 +112,7 @@ bytearray_getbuffer(PyByteArrayObject *obj, Py_buffer *view, int flags)
                 obj->ob_exports++;
                 return 0;
         }
-        if (obj->ob_bytes == NULL)
-                ptr = "";
-        else
-                ptr = obj->ob_bytes;
+        ptr = (void *) PyByteArray_AS_STRING(obj);
         ret = PyBuffer_FillInfo(view, (PyObject*)obj, ptr, Py_SIZE(obj), 0, flags);
         if (ret >= 0) {
                 obj->ob_exports++;
@@ -201,7 +191,7 @@ PyByteArray_FromStringAndSize(const char *bytes, Py_ssize_t size)
             Py_DECREF(new);
             return PyErr_NoMemory();
         }
-        if (bytes != NULL)
+        if (bytes != NULL && size > 0)
             memcpy(new->ob_bytes, bytes, size);
         new->ob_bytes[size] = '\0';  /* Trailing null byte */
     }
@@ -1114,7 +1104,6 @@ bytearray_dealloc(PyByteArrayObject *self)
 #define STRINGLIB_LEN PyByteArray_GET_SIZE
 #define STRINGLIB_STR PyByteArray_AS_STRING
 #define STRINGLIB_NEW PyByteArray_FromStringAndSize
-#define STRINGLIB_EMPTY nullbytes
 #define STRINGLIB_ISSPACE Py_ISSPACE
 #define STRINGLIB_ISLINEBREAK(x) ((x == '\n') || (x == '\r'))
 #define STRINGLIB_CHECK_EXACT PyByteArray_CheckExact