bpo-41252: Fix incorrect refcounting in _ssl.c's _servername_callback() (GH-21407)

(cherry picked from commit ee96f32ca24779656d3c8736d26671fc3689f0a3)

Co-authored-by: Zackery Spytz <zspytz@gmail.com>

diff --git a/Misc/NEWS.d/next/Core and Builtins/2020-07-08-21-55-23.bpo-41252.nBWL-Y.rst b/Misc/NEWS.d/next/Core and Builtins/2020-07-08-21-55-23.bpo-41252.nBWL-Y.rst
new file mode 100644 (file)
index 0000000..65f3189
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2020-07-08-21-55-23.bpo-41252.nBWL-Y.rst
@@ -0,0 +1 @@
+Fix incorrect refcounting in _ssl.c's ``_servername_callback()``.

diff --git a/Modules/_ssl.c b/Modules/_ssl.c
index 8ee2c170368fdbf0cd68f2a99c07f2a08c0414f0..1944393e548908675f774b472f95d4a44a93c191 100644 (file)
--- a/Modules/_ssl.c
+++ b/Modules/_ssl.c
@@ -4548,11 +4548,12 @@ _servername_callback(SSL *s, int *al, void *args)
          * back into a str object, but still as an A-label (bpo-28414)
          */
         servername_str = PyUnicode_FromEncodedObject(servername_bytes, "ascii", NULL);
-        Py_DECREF(servername_bytes);
         if (servername_str == NULL) {
             PyErr_WriteUnraisable(servername_bytes);
+            Py_DECREF(servername_bytes);
             goto error;
         }
+        Py_DECREF(servername_bytes);
         result = PyObject_CallFunctionObjArgs(
             ssl_ctx->set_sni_cb, ssl_socket, servername_str,
             ssl_ctx, NULL);