Re: [PATCH v22 0/8] MR3103: server: Create and use a desktop shared mapping for GetCursorPos.

[Jinoh Kang (＠iamahuman)]

Jinoh Kang (@iamahuman) commented about dlls/win32u/winstation.c:
> +{
> - struct shared_session *session;
> - BOOL valid = TRUE;
> -
> - TRACE( "tid %04x, type %u\n", tid, type );
> -
> - memset( info, 0, sizeof(*info) );
> - info->index = -1;
> -
> - while ((session = get_shared_session( !valid )))
> - {
> -
>    info->session_id = session->id;
> -
>    if ((info->index = get_thread_session_object_index( tid, type, &info->id )) == -1) break;
> -
>    if ((valid = info->index < session->object_capacity)) break;
> -
>    shared_session_release( session );
> - }

We have an out-of-bounds `info->index` left here. If the next iteration's `get_shared_session()` fails, we won't be able to detect this condition; instead, we will return the invalid index (as well as a NULL session) as-is to the caller.

To avoid this, ensure `info->index` is set to the sentinel when the while condition fails...

```suggestion:-1+0
        shared_session_release( session );
        info->index = -1;
    }
```