From 40ca54e3a686f13117f3de0c443f8026dadf7c44 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sat, 27 Jan 2018 10:58:43 -0800 Subject: [PATCH] net_sched: gen_estimator: fix lockdep splat 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 Reported-by: syzbot Acked-by: Cong Wang Signed-off-by: David S. Miller --- net/core/gen_estimator.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/core/gen_estimator.c b/net/core/gen_estimator.c index 9834cfa21b21..0a3f88f08727 100644 --- a/net/core/gen_estimator.c +++ b/net/core/gen_estimator.c @@ -159,7 +159,11 @@ int gen_new_estimator(struct gnet_stats_basic_packed *bstats, est->intvl_log = intvl_log; est->cpu_bstats = cpu_bstats; + if (stats_lock) + local_bh_disable(); est_fetch_counters(est, &b); + if (stats_lock) + local_bh_enable(); est->last_bytes = b.bytes; est->last_packets = b.packets; old = rcu_dereference_protected(*rate_est, 1); -- 2.34.1