linux-kernel - [PATCH 3.16 175/294] sch_hfsc: fix null pointer deref and double free on init failure

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Message-ID: <lsq.1510009382.627736410@decadent.org.uk>
Date:   Mon, 06 Nov 2017 23:03:02 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Nikolay Aleksandrov" <nikolay@...ulusnetworks.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 3.16 175/294] sch_hfsc: fix null pointer deref and double
 free on init failure

3.16.50-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>

commit 3bdac362a2f89ed3e148fa6f38c5f5d858f50b1a upstream.

Depending on where ->init fails we can get a null pointer deref due to
uninitialized hires timer (watchdog) or a double free of the qdisc hash
because it is already freed by ->destroy().

Fixes: 8d5537387505 ("net/sched/hfsc: allocate tcf block for hfsc root class")
Fixes: 87b60cfacf9f ("net_sched: fix error recovery at qdisc creation")
Signed-off-by: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
[bwh: Backported to 3.16: sch_hfsc doesn't use a tcf block]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/net/sched/sch_hfsc.c
+++ b/net/sched/sch_hfsc.c
@@ -1432,6 +1432,8 @@ hfsc_init_qdisc(struct Qdisc *sch, struc
 	struct tc_hfsc_qopt *qopt;
 	int err;
 
+	qdisc_watchdog_init(&q->watchdog, sch);
+
 	if (opt == NULL || nla_len(opt) < sizeof(*qopt))
 		return -EINVAL;
 	qopt = nla_data(opt);
@@ -1457,8 +1459,6 @@ hfsc_init_qdisc(struct Qdisc *sch, struc
 	qdisc_class_hash_insert(&q->clhash, &q->root.cl_common);
 	qdisc_class_hash_grow(sch, &q->clhash);
 
-	qdisc_watchdog_init(&q->watchdog, sch);
-
 	return 0;
 }