On Sat, Jan 27, 2018 at 10:58 AM, Eric Dumazet <[email protected]> wrote: > From: Eric Dumazet <[email protected]> > > 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 <[email protected]> > Reported-by: syzbot <[email protected]>
Acked-by: Cong Wang <[email protected]> Nit: perhaps it is better to move the spin_lock out of est_fetch_counters() and let callers decide to use spin_lock or spin_lock_bh.
