4.15-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
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 edumazet@google.com Reported-by: syzbot syzkaller@googlegroups.com Acked-by: Cong Wang xiyou.wangcong@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- net/core/gen_estimator.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/net/core/gen_estimator.c +++ b/net/core/gen_estimator.c @@ -159,7 +159,11 @@ int gen_new_estimator(struct gnet_stats_ 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);