Prior to this patch, the following fails, but at least seems to give a sensible error: $ nbdsh -c 'nbd.Buffer.from_bytearray(b"1"*8)' Traceback (most recent call last): File "/usr/lib64/python3.10/runpy.py", line 196, in _run_module_as_main return _run_code(code, main_globals, None, File "/usr/lib64/python3.10/runpy.py", line 86, in _run_code exec(code, run_globals) File "/usr/lib64/python3.10/site-packages/nbd.py", line 2726, in <module> nbdsh.shell() File "/usr/lib64/python3.10/site-packages/nbdsh.py", line 139, in shell exec(c, d, d) File "<string>", line 1, in <module> File "/usr/lib64/python3.10/site-packages/nbd.py", line 132, in from_bytearray o = libnbdmod.aio_buffer_from_bytearray(ba) RuntimeError: parameter is not a bytearray while this version 1 byte longer flat out segfaults: $ nbdsh -c 'nbd.Buffer.from_bytearray(b"1"*9)' and this one is subtly different: $ nbdsh -c 'nbd.Buffer.from_bytearray(h)' Traceback (most recent call last): ... File "/usr/lib64/python3.10/site-packages/nbd.py", line 132, in from_bytearray o = libnbdmod.aio_buffer_from_bytearray(ba) MemoryError That's because PyByteArray_AsString() blindly assumes that its argument is a PyByteArray, and goes haywire when it is not, unless we got lucky that the incorrectly-typed object behaves similarly enough (which, for byte literals, is size-dependent). But Python already has a handy way to convert any object that supports the buffer interface into a bytearray. Using it, we can now support many more parameters; passing in b"1"*9 now correctly creates a 9-byte buffer rather than failing. And the error message for a non-buffer also improves: $ ./run nbdsh -c 'nbd.Buffer.from_bytearray(h)' Traceback (most recent call last): ... File "/home/eblake/libnbd/python/nbd.py", line 132, in from_bytearray o = libnbdmod.aio_buffer_from_bytearray(ba) TypeError: cannot convert 'NBD' object to bytearray (A reliable TypeError is always better than an unexpected MemoryError or segfault). --- python/handle.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/python/handle.c b/python/handle.c index 9c08dc1..9fe3f8e 100644 --- a/python/handle.c +++ b/python/handle.c @@ -1,5 +1,5 @@ /* NBD client library in userspace - * Copyright (C) 2013-2020 Red Hat Inc. + * Copyright (C) 2013-2022 Red Hat Inc. * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public @@ -159,6 +159,7 @@ PyObject * nbd_internal_py_aio_buffer_from_bytearray (PyObject *self, PyObject *args) { PyObject *obj; + PyObject *arr = NULL; Py_ssize_t len; void *data; struct py_aio_buffer *buf; @@ -169,9 +170,17 @@ nbd_internal_py_aio_buffer_from_bytearray (PyObject *self, PyObject *args) &obj)) return NULL; + if (! PyByteArray_Check (obj)) { + arr = PyByteArray_FromObject (obj); + if (arr == NULL) + return NULL; + obj = arr; + } data = PyByteArray_AsString (obj); if (!data) { - PyErr_SetString (PyExc_RuntimeError, "parameter is not a bytearray"); + PyErr_SetString (PyExc_RuntimeError, + "parameter is not a bytearray or buffer"); + Py_XDECREF (arr); return NULL; } len = PyByteArray_Size (obj); @@ -179,6 +188,7 @@ nbd_internal_py_aio_buffer_from_bytearray (PyObject *self, PyObject *args) buf = malloc (sizeof *buf); if (buf == NULL) { PyErr_NoMemory (); + Py_XDECREF (arr); return NULL; } @@ -187,9 +197,11 @@ nbd_internal_py_aio_buffer_from_bytearray (PyObject *self, PyObject *args) if (buf->data == NULL) { PyErr_NoMemory (); free (buf); + Py_XDECREF (arr); return NULL; } memcpy (buf->data, data, len); + Py_XDECREF (arr); ret = PyCapsule_New (buf, aio_buffer_name, free_aio_buffer); if (ret == NULL) {