From 14b2ad0bb2fa7bbc5b5b90ec3b3b3e7a68aa10c2 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 commit 40ca54e3a686f13117f3de0c443f8026dadf7c44 upstream. 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 Signed-off-by: Greg Kroah-Hartman --- 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 7c1ffd6f9501..00ecec4891f3 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); -- 2.20.1