netdev - [patch net 1/2] net: sched: fix clsact init error path

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Date:   Fri, 15 Dec 2017 12:40:12 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     netdev@...r.kernel.org
Cc:     davem@...emloft.net, jhs@...atatu.com, xiyou.wangcong@...il.com,
        mlxsw@...lanox.com, daniel@...earbox.net
Subject: [patch net 1/2] net: sched: fix clsact init error path

From: Jiri Pirko <jiri@...lanox.com>

Since in qdisc_create, the destroy op is called when init fails, we
don't do cleanup in init and leave it up to destroy.
This fixes use-after-free when trying to put already freed block.

Fixes: 6e40cf2d4dee ("net: sched: use extended variants of block_get/put in ingress and clsact qdiscs")
Signed-off-by: Jiri Pirko <jiri@...lanox.com>
---
 net/sched/cls_api.c     | 4 ++--
 net/sched/sch_ingress.c | 6 +-----
 2 files changed, 3 insertions(+), 7 deletions(-)

diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index f40256a..b91ea03 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -351,6 +351,8 @@ void tcf_block_put_ext(struct tcf_block *block, struct Qdisc *q,
 {
 	struct tcf_chain *chain;
 
+	if (!block)
+		return;
 	/* Hold a refcnt for all chains, except 0, so that they don't disappear
 	 * while we are iterating.
 	 */
@@ -377,8 +379,6 @@ void tcf_block_put(struct tcf_block *block)
 {
 	struct tcf_block_ext_info ei = {0, };
 
-	if (!block)
-		return;
 	tcf_block_put_ext(block, block->q, &ei);
 }
 
diff --git a/net/sched/sch_ingress.c b/net/sched/sch_ingress.c
index 5ecc38f..5e1cd2e 100644
--- a/net/sched/sch_ingress.c
+++ b/net/sched/sch_ingress.c
@@ -190,7 +190,7 @@ static int clsact_init(struct Qdisc *sch, struct nlattr *opt)
 
 	err = tcf_block_get_ext(&q->egress_block, sch, &q->egress_block_info);
 	if (err)
-		goto err_egress_block_get;
+		return err;
 
 	net_inc_ingress_queue();
 	net_inc_egress_queue();
@@ -198,10 +198,6 @@ static int clsact_init(struct Qdisc *sch, struct nlattr *opt)
 	sch->flags |= TCQ_F_CPUSTATS;
 
 	return 0;
-
-err_egress_block_get:
-	tcf_block_put_ext(q->ingress_block, sch, &q->ingress_block_info);
-	return err;
 }
 
 static void clsact_destroy(struct Qdisc *sch)
-- 
2.9.5