netdev - [patch net-next v2] net: sched: silence uninitialized parent variable warning in tc_dump

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Date:   Thu, 18 Jan 2018 16:14:49 +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, sfr@...b.auug.org.au, arnd@...db.de
Subject: [patch net-next v2] net: sched: silence uninitialized parent variable warning in tc_dump_tfilter

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

When tcm->tcm_ifindex == TCM_IFINDEX_MAGIC_BLOCK, parent is still passed
down but the value is never used. Compiler does not recognize it and
issues a warning. Silence it down initializing parent to 0.

Fixes: 7960d1daf278 ("net: sched: use block index as a handle instead of qdisc when block is shared")
Reported-by: David Miller <davem@...emloft.net>
Reported-by: Stephen Rothwell <sfr@...b.auug.org.au>
Signed-off-by: Jiri Pirko <jiri@...lanox.com>
---
v1->v2:
- add comment about why the initialization to 0 is ok
- move the initialization into the if block to be near the comment
---
 net/sched/cls_api.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index e500d11da9cd..86d6e9d2cf00 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -1317,6 +1317,13 @@ static int tc_dump_tfilter(struct sk_buff *skb, struct netlink_callback *cb)
 		block = tcf_block_lookup(net, tcm->tcm_block_index);
 		if (!block)
 			goto out;
+		/* If we work with block index, q is NULL and parent value
+		 * will never be used in the following code. The check
+		 * in tcf_fill_node prevents it. However, compiler does not
+		 * see that far, so set parent to zero to silence the warning
+		 * about parent being uninitialized.
+		 */
+		parent = 0;
 	} else {
 		const struct Qdisc_class_ops *cops;
 		struct net_device *dev;
-- 
2.14.3