Libguestfs - Jun 2022 - [libnbd PATCH 1/5] python: Avoid memleak on (unlikely) module failure

Python 3.10 added PyModule_AddObjectRef() to more easily avoid a
common memory leak when ading to a module fails (unlikely in our case,
since we initialize early in the python process, but still something
we must worry about for corner-case correctness).  But since we target
older Python, we must check for errors and clean up ourselves.

Fixes: 259d46cb ("python: Raise a custome exception containing error string
and errno.", v0.1.6)
---
 generator/Python.ml | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/generator/Python.ml b/generator/Python.ml
index 1c4446e..3f672ba 100644
--- a/generator/Python.ml
+++ b/generator/Python.ml
@@ -143,9 +143,11 @@ let
     return NULL;

   nbd_internal_py_Error = PyErr_NewException (\"nbd.Error\", NULL,
NULL);
-  if (nbd_internal_py_Error == NULL)
+  if (PyModule_AddObject (mod, \"Error\", nbd_internal_py_Error) <
0) {
+    Py_XDECREF (nbd_internal_py_Error);
+    Py_DECREF (mod);
     return NULL;
-  PyModule_AddObject (mod, \"Error\", nbd_internal_py_Error);
+  }

   return mod;
 }
-- 
2.36.1

On Fri, Jun 03, 2022 at 05:26:31PM -0500, Eric Blake
wrote:
> Python 3.10 added PyModule_AddObjectRef() to more easily avoid a
> common memory leak when ading to a module fails (unlikely in our case,
> since we initialize early in the python process, but still something
> we must worry about for corner-case correctness).  But since we target
> older Python, we must check for errors and clean up ourselves.
> 
> Fixes: 259d46cb ("python: Raise a custome exception containing error
string and errno.", v0.1.6)
> ---
>  generator/Python.ml | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/generator/Python.ml b/generator/Python.ml
> index 1c4446e..3f672ba 100644
> --- a/generator/Python.ml
> +++ b/generator/Python.ml
> @@ -143,9 +143,11 @@ let
>      return NULL;
> 
>    nbd_internal_py_Error = PyErr_NewException (\"nbd.Error\",
NULL, NULL);
> -  if (nbd_internal_py_Error == NULL)
> +  if (PyModule_AddObject (mod, \"Error\", nbd_internal_py_Error)
< 0) {
> +    Py_XDECREF (nbd_internal_py_Error);
> +    Py_DECREF (mod);
>      return NULL;
> -  PyModule_AddObject (mod, \"Error\", nbd_internal_py_Error);
> +  }
> 
Reviewed-by: Richard W.M. Jones <rjones at redhat.com>

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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