From: Cong Wang <xiyou.wangcong@gmail.com>
Date: Thu, 2 Nov 2017 17:32:08 -0700
Subject: net_sched: check NULL in tcf_block_put()
Patch-mainline: v4.15-rc1
Git-commit: 8f918d3ff4a1283a1693afe2b4c8e1844674ca15
References: bsc#1109837

Callers of tcf_block_put() could pass NULL so
we can't use block->q before checking if block is
NULL or not.

tcf_block_put_ext() callers are fine, it is always
non-NULL.

Fixes: 8c4083b30e56 ("net: sched: add block bind/unbind notif. and extended block_get/put")
Reported-by: Dave Taht <dave.taht@gmail.com>
Cc: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/sched/cls_api.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -365,9 +365,6 @@ void tcf_block_put_ext(struct tcf_block
 		       struct tcf_proto __rcu **p_filter_chain, struct Qdisc *q,
 		       struct tcf_block_ext_info *ei)
 {
-	if (!block)
-		return;
-
 	tcf_block_offload_unbind(block, q, ei);
 
 	INIT_WORK(&block->work, tcf_block_put_deferred);
@@ -384,6 +381,8 @@ void tcf_block_put(struct tcf_block *blo
 {
 	struct tcf_block_ext_info ei = {0, };
 
+	if (!block)
+		return;
 	tcf_block_put_ext(block, NULL, block->q, &ei);
 }
 EXPORT_SYMBOL(tcf_block_put);