netdev - [PATCH net] mctp: Fix incorrect netdev unref for extended addr

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Message-Id: <20220218051918.1914025-1-matt@codeconstruct.com.au>
Date:   Fri, 18 Feb 2022 13:19:18 +0800
From:   Matt Johnston <matt@...econstruct.com.au>
To:     unlisted-recipients:; (no To-header on input)
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jeremy Kerr <jk@...econstruct.com.au>
Subject: [PATCH net] mctp: Fix incorrect netdev unref for extended addr

In the extended addressing local route output codepath
dev_get_by_index_rcu() doesn't take a dev_hold() so we shouldn't
dev_put(). Instead we need to hold/put the mctp_dev.

Fixes: 2a98db59117e ("mctp: Implement extended addressing")
Signed-off-by: Matt Johnston <matt@...econstruct.com.au>
---
 net/mctp/route.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/net/mctp/route.c b/net/mctp/route.c
index e52cef750500..6ef79ab4a076 100644
--- a/net/mctp/route.c
+++ b/net/mctp/route.c
@@ -786,9 +786,8 @@ int mctp_local_output(struct sock *sk, struct mctp_route *rt,
 {
 	struct mctp_sock *msk = container_of(sk, struct mctp_sock, sk);
 	struct mctp_skb_cb *cb = mctp_cb(skb);
-	struct mctp_route tmp_rt;
+	struct mctp_route tmp_rt = {0};
 	struct mctp_sk_key *key;
-	struct net_device *dev;
 	struct mctp_hdr *hdr;
 	unsigned long flags;
 	unsigned int mtu;
@@ -801,12 +800,12 @@ int mctp_local_output(struct sock *sk, struct mctp_route *rt,
 
 	if (rt) {
 		ext_rt = false;
-		dev = NULL;
-
 		if (WARN_ON(!rt->dev))
 			goto out_release;
 
 	} else if (cb->ifindex) {
+		struct net_device *dev;
+
 		ext_rt = true;
 		rt = &tmp_rt;
 
@@ -816,8 +815,9 @@ int mctp_local_output(struct sock *sk, struct mctp_route *rt,
 			rcu_read_unlock();
 			return rc;
 		}
-
 		rt->dev = __mctp_dev_get(dev);
+		if (rt->dev)
+			mctp_dev_hold(rt->dev);
 		rcu_read_unlock();
 
 		if (!rt->dev)
@@ -891,10 +891,10 @@ int mctp_local_output(struct sock *sk, struct mctp_route *rt,
 	if (!ext_rt)
 		mctp_route_release(rt);
 
-	dev_put(dev);
+	if (tmp_rt.dev)
+		mctp_dev_put(tmp_rt.dev);
 
 	return rc;
-
 }
 
 /* route management */
-- 
2.32.0