gh-94101 Disallow instantiation of SSLSession objects (GH-94102)

Fixes #94101

Automerge-Triggered-By: GH:tiran

Author: chgnrdv

Misc/NEWS.d/next/Library/2022-06-22-11-16-11.gh-issue-94101.V9vDG8.rst

@@ -0,0 +1,3 @@
+Manual instantiation of :class:`ssl.SSLSession` objects is no longer allowed
+as it lead to misconfigured instances that crashed the interpreter when
+attributes where accessed on them.

Modules/_ssl.c

@@ -5067,7 +5067,8 @@ static PyType_Spec PySSLSession_spec = {
     .name = "_ssl.SSLSession",
     .basicsize = sizeof(PySSLSession),
     .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
-              Py_TPFLAGS_IMMUTABLETYPE),
+              Py_TPFLAGS_IMMUTABLETYPE |
+              Py_TPFLAGS_DISALLOW_INSTANTIATION),
     .slots = PySSLSession_slots,
 };