linux-kernel - [PATCH net,v2] net: sched: tbf: don't call qdisc

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Message-ID: <20220826013930.340121-1-shaozhengchao@huawei.com>
Date:   Fri, 26 Aug 2022 09:39:30 +0800
From:   Zhengchao Shao <shaozhengchao@...wei.com>
To:     <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
        <pabeni@...hat.com>, <jhs@...atatu.com>,
        <xiyou.wangcong@...il.com>, <jiri@...nulli.us>
CC:     <vladbu@...lanox.com>, <weiyongjun1@...wei.com>,
        <yuehaibing@...wei.com>, <shaozhengchao@...wei.com>
Subject: [PATCH net,v2] net: sched: tbf: don't call qdisc_put() while holding tree lock

The issue is the same to commit c2999f7fb05b ("net: sched: multiq: don't
call qdisc_put() while holding tree lock"). Qdiscs call qdisc_put() while
holding sch tree spinlock, which results sleeping-while-atomic BUG.

Fixes: c266f64dbfa2 ("net: sched: protect block state with mutex")
Signed-off-by: Zhengchao Shao <shaozhengchao@...wei.com>
---
v1: The subject needs to be changed to [PATCH net].
---
 net/sched/sch_tbf.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/sched/sch_tbf.c b/net/sched/sch_tbf.c
index 72102277449e..36079fdde2cb 100644
--- a/net/sched/sch_tbf.c
+++ b/net/sched/sch_tbf.c
@@ -356,6 +356,7 @@ static int tbf_change(struct Qdisc *sch, struct nlattr *opt,
 	struct nlattr *tb[TCA_TBF_MAX + 1];
 	struct tc_tbf_qopt *qopt;
 	struct Qdisc *child = NULL;
+	struct Qdisc *old = NULL;
 	struct psched_ratecfg rate;
 	struct psched_ratecfg peak;
 	u64 max_size;
@@ -447,7 +448,7 @@ static int tbf_change(struct Qdisc *sch, struct nlattr *opt,
 	sch_tree_lock(sch);
 	if (child) {
 		qdisc_tree_flush_backlog(q->qdisc);
-		qdisc_put(q->qdisc);
+		old = q->qdisc;
 		q->qdisc = child;
 	}
 	q->limit = qopt->limit;
@@ -467,6 +468,7 @@ static int tbf_change(struct Qdisc *sch, struct nlattr *opt,
 	memcpy(&q->peak, &peak, sizeof(struct psched_ratecfg));
 
 	sch_tree_unlock(sch);
+	qdisc_put(old);
 	err = 0;
 
 	tbf_offload_change(sch);
-- 
2.17.1