From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH net] net_sched: gen_estimator: fix lockdep splat
Date: Mon, 29 Jan 2018 14:31:08 -0500 (EST)
Message-ID: <20180129.143108.1563505447234447053.davem@davemloft.net>
References: <1517079523.3715.73.camel@gmail.com>
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To: eric.dumazet@gmail.com
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From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Sat, 27 Jan 2018 10:58:43 -0800

> From: Eric Dumazet <edumazet@google.com>
> 
> syzbot reported a lockdep splat in gen_new_estimator() /
> est_fetch_counters() when attempting to lock est->stats_lock.
> 
> Since est_fetch_counters() is called from BH context from timer
> interrupt, we need to block BH as well when calling it from process
> context.
> 
> Most qdiscs use per cpu counters and are immune to the problem,
> but net/sched/act_api.c and net/netfilter/xt_RATEEST.c are using
> a spinlock to protect their data. They both call gen_new_estimator()
> while object is created and not yet alive, so this bug could
> not trigger a deadlock, only a lockdep splat.
> 
> Fixes: 1c0d32fde5bd ("net_sched: gen_estimator: complete rewrite of rate estimators")
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Reported-by: syzbot <syzkaller@googlegroups.com>

Applied, thanks.