linux-kernel - [PATCH] [net-next] net: sched: avoid uninitialized variable use

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Message-Id: <20180118131747.920324-1-arnd@arndb.de>
Date:   Thu, 18 Jan 2018 14:17:28 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        "David S. Miller" <davem@...emloft.net>
Cc:     Arnd Bergmann <arnd@...db.de>,
        David Ahern <dsa@...ulusnetworks.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] [net-next] net: sched: avoid uninitialized variable use

gcc has identified a code path in which we pass uninitialized
data into tc_dump_tfilter():

net/sched/cls_api.c: In function 'tc_dump_tfilter':
net/sched/cls_api.c:1268:8: error: 'parent' may be used uninitialized in this function [-Werror=maybe-uninitialized]

This initializes the variable to the value it had before the previous
change.

Fixes: 7960d1daf278 ("net: sched: use block index as a handle instead of qdisc when block is shared")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
----
I don't know if my patch is the best way to address the issue, but
if not, then at least it helps show what the warning is about
and lets someone else come up with a better solution.
---
 net/sched/cls_api.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index e500d11da9cd..a95bfc8fc442 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -1317,6 +1317,7 @@ 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;
+		parent = tcm->tcm_parent;
 	} else {
 		const struct Qdisc_class_ops *cops;
 		struct net_device *dev;
-- 
2.9.0