linux-kernel - [PATCH net-next 2/2] net: sched: htb: remove redundant resource cleanup in htb

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Date:   Tue, 30 Aug 2022 08:56:38 +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:     <weiyongjun1@...wei.com>, <yuehaibing@...wei.com>,
        <shaozhengchao@...wei.com>
Subject: [PATCH net-next 2/2] net: sched: htb: remove redundant resource cleanup in htb_init()

If htb_init() fails, qdisc_create() invokes htb_destroy() to clear
resources. Therefore, remove redundant resource cleanup in htb_init().

Signed-off-by: Zhengchao Shao <shaozhengchao@...wei.com>
---
 net/sched/sch_htb.c | 36 +++++++++---------------------------
 1 file changed, 9 insertions(+), 27 deletions(-)

diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index cb5872d22ecf..da75885bbffd 100644
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -1102,7 +1102,7 @@ static int htb_init(struct Qdisc *sch, struct nlattr *opt,
 
 	err = qdisc_class_hash_init(&q->clhash);
 	if (err < 0)
-		goto err_free_direct_qdiscs;
+		return err;
 
 	qdisc_skb_head_init(&q->direct_queue);
 
@@ -1125,8 +1125,7 @@ static int htb_init(struct Qdisc *sch, struct nlattr *opt,
 		qdisc = qdisc_create_dflt(dev_queue, &pfifo_qdisc_ops,
 					  TC_H_MAKE(sch->handle, 0), extack);
 		if (!qdisc) {
-			err = -ENOMEM;
-			goto err_free_qdiscs;
+			return -ENOMEM;
 		}
 
 		htb_set_lockdep_class_child(qdisc);
@@ -1144,7 +1143,7 @@ static int htb_init(struct Qdisc *sch, struct nlattr *opt,
 	};
 	err = htb_offload(dev, &offload_opt);
 	if (err)
-		goto err_free_qdiscs;
+		return err;
 
 	/* Defer this assignment, so that htb_destroy skips offload-related
 	 * parts (especially calling ndo_setup_tc) on errors.
@@ -1152,22 +1151,6 @@ static int htb_init(struct Qdisc *sch, struct nlattr *opt,
 	q->offload = true;
 
 	return 0;
-
-err_free_qdiscs:
-	for (ntx = 0; ntx < q->num_direct_qdiscs && q->direct_qdiscs[ntx];
-	     ntx++)
-		qdisc_put(q->direct_qdiscs[ntx]);
-
-	qdisc_class_hash_destroy(&q->clhash);
-	/* Prevent use-after-free and double-free when htb_destroy gets called.
-	 */
-	q->clhash.hash = NULL;
-	q->clhash.hashsize = 0;
-
-err_free_direct_qdiscs:
-	kfree(q->direct_qdiscs);
-	q->direct_qdiscs = NULL;
-	return err;
 }
 
 static void htb_attach_offload(struct Qdisc *sch)
@@ -1690,13 +1673,12 @@ static void htb_destroy(struct Qdisc *sch)
 	qdisc_class_hash_destroy(&q->clhash);
 	__qdisc_reset_queue(&q->direct_queue);
 
-	if (!q->offload)
-		return;
-
-	offload_opt = (struct tc_htb_qopt_offload) {
-		.command = TC_HTB_DESTROY,
-	};
-	htb_offload(dev, &offload_opt);
+	if (q->offload) {
+		offload_opt = (struct tc_htb_qopt_offload) {
+			.command = TC_HTB_DESTROY,
+		};
+		htb_offload(dev, &offload_opt);
+	}
 
 	if (!q->direct_qdiscs)
 		return;
-- 
2.17.1