linux-kernel - [PATCH 5.7 011/244] net_sched: fix a memory leak in atm_tc

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Message-Id: <20200720152826.411450269@linuxfoundation.org>
Date:   Mon, 20 Jul 2020 17:34:42 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jamal Hadi Salim <jhs@...atatu.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Cong Wang <xiyou.wangcong@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        syzbot+d411cff6ab29cc2c311b@...kaller.appspotmail.com
Subject: [PATCH 5.7 011/244] net_sched: fix a memory leak in atm_tc_init()

From: Cong Wang <xiyou.wangcong@...il.com>

[ Upstream commit 306381aec7c2b5a658eebca008c8a1b666536cba ]

When tcf_block_get() fails inside atm_tc_init(),
atm_tc_put() is called to release the qdisc p->link.q.
But the flow->ref prevents it to do so, as the flow->ref
is still zero.

Fix this by moving the p->link.ref initialization before
tcf_block_get().

Fixes: 6529eaba33f0 ("net: sched: introduce tcf block infractructure")
Reported-and-tested-by: syzbot+d411cff6ab29cc2c311b@...kaller.appspotmail.com
Cc: Jamal Hadi Salim <jhs@...atatu.com>
Cc: Jiri Pirko <jiri@...nulli.us>
Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/sched/sch_atm.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/net/sched/sch_atm.c
+++ b/net/sched/sch_atm.c
@@ -553,16 +553,16 @@ static int atm_tc_init(struct Qdisc *sch
 	if (!p->link.q)
 		p->link.q = &noop_qdisc;
 	pr_debug("atm_tc_init: link (%p) qdisc %p\n", &p->link, p->link.q);
+	p->link.vcc = NULL;
+	p->link.sock = NULL;
+	p->link.common.classid = sch->handle;
+	p->link.ref = 1;
 
 	err = tcf_block_get(&p->link.block, &p->link.filter_list, sch,
 			    extack);
 	if (err)
 		return err;
 
-	p->link.vcc = NULL;
-	p->link.sock = NULL;
-	p->link.common.classid = sch->handle;
-	p->link.ref = 1;
 	tasklet_init(&p->task, sch_atm_dequeue, (unsigned long)sch);
 	return 0;
 }