Race condition in OpenBSD VFS allows local users to cause a denial of service (kernel panic) by (1) creating a pipe in one thread and causi…

Race condition in OpenBSD VFS allows local users to cause a denial of service (kernel panic) by (1) creating a pipe in one thread and causing another thread to set one of the file descriptors to NULL via a close, or (2) calling dup2 on a file descriptor in one process, then setting the descriptor to NULL via a close in another process that is created via rfork.