bpo-42924: Fix incorrect copy in bytearray_repeat (GH-24208)

Before, using the * operator to repeat a bytearray would copy data from the start of
the internal buffer (ob_bytes) and not from the start of the actual data (ob_start).

1 files changed, 4 insertions, 2 deletions

diff --git a/Objects/bytearrayobject.c b/Objects/bytearrayobject.c
index 7cb2b1478cf..2eaca5cec42 100644
--- a/Objects/bytearrayobject.c
+++ b/Objects/bytearrayobject.c
@@ -321,6 +321,7 @@ bytearray_repeat(PyByteArrayObject *self, Py_ssize_t count)
     PyByteArrayObject *result;
     Py_ssize_t mysize;
     Py_ssize_t size;
+    const char *buf;
 
     if (count < 0)
         count = 0;
@@ -329,13 +330,14 @@ bytearray_repeat(PyByteArrayObject *self, Py_ssize_t count)
         return PyErr_NoMemory();
     size = mysize * count;
     result = (PyByteArrayObject *)PyByteArray_FromStringAndSize(NULL, size);
+    buf = PyByteArray_AS_STRING(self);
     if (result != NULL && size != 0) {
         if (mysize == 1)
-            memset(result->ob_bytes, self->ob_bytes[0], size);
+            memset(result->ob_bytes, buf[0], size);
         else {
             Py_ssize_t i;
             for (i = 0; i < count; i++)
-                memcpy(result->ob_bytes + i*mysize, self->ob_bytes, mysize);
+                memcpy(result->ob_bytes + i*mysize, buf, mysize);
         }
     }
     return (PyObject *)result;