From: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Date: Tue, 15 Aug 2017 16:35:21 +0300
Subject: net_sched: reset pointers to tcf blocks in classful qdiscs'
 destructors
Patch-mainline: v4.13-rc6
Git-commit: 898904226b5a6dee657f23cf51e385f50da22596
References: bsc#1056787

Traffic filters could keep direct pointers to classes in classful qdisc,
thus qdisc destruction first removes all filters before freeing classes.
Class destruction methods also tries to free attached filters but now
this isn't safe because tcf_block_put() unlike to tcf_destroy_chain()
cannot be called second time.

This patch set class->block to NULL after first tcf_block_put() and
turn second call into no-op.

Fixes: 6529eaba33f0 ("net: sched: introduce tcf block infractructure")
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/sched/sch_atm.c  |    4 +++-
 net/sched/sch_cbq.c  |    4 +++-
 net/sched/sch_hfsc.c |    4 +++-
 net/sched/sch_htb.c  |    4 +++-
 4 files changed, 12 insertions(+), 4 deletions(-)

--- a/net/sched/sch_atm.c
+++ b/net/sched/sch_atm.c
@@ -572,8 +572,10 @@ static void atm_tc_destroy(struct Qdisc
 	struct atm_flow_data *flow, *tmp;
 
 	pr_debug("atm_tc_destroy(sch %p,[qdisc %p])\n", sch, p);
-	list_for_each_entry(flow, &p->flows, list)
+	list_for_each_entry(flow, &p->flows, list) {
 		tcf_block_put(flow->block);
+		flow->block = NULL;
+	}
 
 	list_for_each_entry_safe(flow, tmp, &p->flows, list) {
 		if (flow->ref > 1)
--- a/net/sched/sch_cbq.c
+++ b/net/sched/sch_cbq.c
@@ -1431,8 +1431,10 @@ static void cbq_destroy(struct Qdisc *sc
 	 * be bound to classes which have been destroyed already. --TGR '04
 	 */
 	for (h = 0; h < q->clhash.hashsize; h++) {
-		hlist_for_each_entry(cl, &q->clhash.hash[h], common.hnode)
+		hlist_for_each_entry(cl, &q->clhash.hash[h], common.hnode) {
 			tcf_block_put(cl->block);
+			cl->block = NULL;
+		}
 	}
 	for (h = 0; h < q->clhash.hashsize; h++) {
 		hlist_for_each_entry_safe(cl, next, &q->clhash.hash[h],
--- a/net/sched/sch_hfsc.c
+++ b/net/sched/sch_hfsc.c
@@ -1530,8 +1530,10 @@ hfsc_destroy_qdisc(struct Qdisc *sch)
 	unsigned int i;
 
 	for (i = 0; i < q->clhash.hashsize; i++) {
-		hlist_for_each_entry(cl, &q->clhash.hash[i], cl_common.hnode)
+		hlist_for_each_entry(cl, &q->clhash.hash[i], cl_common.hnode) {
 			tcf_block_put(cl->block);
+			cl->block = NULL;
+		}
 	}
 	for (i = 0; i < q->clhash.hashsize; i++) {
 		hlist_for_each_entry_safe(cl, next, &q->clhash.hash[i],
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -1258,8 +1258,10 @@ static void htb_destroy(struct Qdisc *sc
 	tcf_block_put(q->block);
 
 	for (i = 0; i < q->clhash.hashsize; i++) {
-		hlist_for_each_entry(cl, &q->clhash.hash[i], common.hnode)
+		hlist_for_each_entry(cl, &q->clhash.hash[i], common.hnode) {
 			tcf_block_put(cl->block);
+			cl->block = NULL;
+		}
 	}
 	for (i = 0; i < q->clhash.hashsize; i++) {
 		hlist_for_each_entry_safe(cl, next, &q->clhash.hash[i],