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

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Date:   Fri, 8 Sep 2017 07:06:10 +0200
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     davem@...emloft.net, ast@...com, john.fastabend@...il.com,
        andy@...yhouse.net, netdev@...r.kernel.org, brouer@...hat.com
Subject: Re: [PATCH net] bpf: don't select potentially stale ri->map from
 buggy xdp progs

On Fri,  8 Sep 2017 00:14:51 +0200
Daniel Borkmann <daniel@...earbox.net> 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