netdev - Re: RCU callback crashes

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Date:   Thu, 21 Dec 2017 13:45:11 -0800
From:   Jakub Kicinski <kubakici@...pl>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     John Fastabend <john.fastabend@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: RCU callback crashes

On Thu, 21 Dec 2017 13:31:01 -0800, Cong Wang wrote:
> >    629          if (likely(skb)) {
> >    630                  qdisc_qstats_cpu_backlog_dec(qdisc, skb);
> >    631                  qdisc_bstats_cpu_update(qdisc, skb);
> >    632                  qdisc_qstats_cpu_qlen_dec(qdisc);
> >    633          }
> >    634
> >    635          return skb;
> >    636  }  
> 
> Hi, Jakub
> 
> Could you test the attached patch? It looks like the __skb_array_empty()
> use is unsafe.

I don't have a reproducer, unfortunately, I haven't seen the splat
since :(  FWIW the kernel config was with all debug/checks disabled,
only KASAN on.