Subject: Re: [PATCH net] bpf: don't select potentially stale ri->map from buggy xdp progs

From: Jesper Dangaard Brouer <[email-masked]>
Date: Fri, 8 Sep 2017 07:06:10 +0200

On Fri,  8 Sep 2017 00:14:51 +0200
Daniel Borkmann <[email-masked]> wrote:

> +	/* This is really only caused by a deliberately crappy
> +	 * BPF program, normally we would never hit that case,
> +	 * so no need to inform someone via tracepoints either,
> +	 * just bail out.
> +	 */
> +	if (unlikely(map_owner != xdp_prog))
> +		return -EINVAL;

IMHO we do need to call the tracepoint here.  It is not just crappy
BPF-progs that cause this situation, it is also drivers not implementing
XDP_REDIRECT yet (which is all but ixgbe).  Due to the level XDP
operates at, tracepoints are the only way users can runtime troubleshoot
their XDP programs.

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer