bpo-34824: Fix a possible NULL pointer dereference in _ssl.c (GH-9606)



On failure, _PyBytes_Resize() will deallocate the bytes object and set
"result" to NULL.


https://bugs.python.org/issue34824
diff --git a/Modules/_ssl.c b/Modules/_ssl.c
index 96bdac4..93498f4 100644
--- a/Modules/_ssl.c
+++ b/Modules/_ssl.c
@@ -4710,12 +4710,17 @@
         return result;
 
     nbytes = BIO_read(self->bio, PyBytes_AS_STRING(result), len);
-    /* There should never be any short reads but check anyway. */
-    if ((nbytes < len) && (_PyBytes_Resize(&result, len) < 0)) {
+    if (nbytes < 0) {
         Py_DECREF(result);
+        _setSSLError(NULL, 0, __FILE__, __LINE__);
         return NULL;
     }
 
+    /* There should never be any short reads but check anyway. */
+    if (nbytes < len) {
+        _PyBytes_Resize(&result, nbytes);
+    }
+
     return result;
 }