[RH7] ms/net_sched: gen_estimator: fix lockdep splat

Submitted by Vasily Averin on Dec. 1, 2020, 8:41 a.m.


Message ID 8c2d7b0a-7aba-863f-1c5a-4ad336ad94d4@virtuozzo.com
State New
Series "ms/net_sched: gen_estimator: fix lockdep splat"
Headers show

Commit Message

Vasily Averin Dec. 1, 2020, 8:41 a.m.
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

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>

(cherry-picked from commit 40ca54e3a686f13117f3de0c443f8026dadf7c44)
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
 net/core/gen_estimator.c | 4 ++++
 1 file changed, 4 insertions(+)

Patch hide | download patch | download mbox

diff --git a/net/core/gen_estimator.c b/net/core/gen_estimator.c
index bca1d06..0e3024c 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);