netdev - [PATCH net-next] llc: fix netdevice reference leaks in llc_ui

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Message-Id: <20220323004147.1990845-1-eric.dumazet@gmail.com>
Date:   Tue, 22 Mar 2022 17:41:47 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        赵子轩 <beraphin@...il.com>,
        Stoyan Manolov <smanolov@...e.de>
Subject: [PATCH net-next] llc: fix netdevice reference leaks in llc_ui_bind()

From: Eric Dumazet <edumazet@...gle.com>

Whenever llc_ui_bind() and/or llc_ui_autobind()
took a reference on a netdevice but subsequently fail,
they must properly release their reference
or risk the infamous message from unregister_netdevice()
at device dismantle.

unregister_netdevice: waiting for eth0 to become free. Usage count = 3

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Reported-by: 赵子轩 <beraphin@...il.com>
Reported-by: Stoyan Manolov <smanolov@...e.de>
---

This can be applied on net tree, depending on how network maintainers
plan to push the fix to Linus, this is obviously a stable candidate.

 net/llc/af_llc.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/llc/af_llc.c b/net/llc/af_llc.c
index 26c00ebf4fbae4d7dc1c27d180385470fa252be0..c86256064743523f0621f21d5d023956cf1df9a0 100644
--- a/net/llc/af_llc.c
+++ b/net/llc/af_llc.c
@@ -311,6 +311,10 @@ static int llc_ui_autobind(struct socket *sock, struct sockaddr_llc *addr)
 	sock_reset_flag(sk, SOCK_ZAPPED);
 	rc = 0;
 out:
+	if (rc) {
+		dev_put_track(llc->dev, &llc->dev_tracker);
+		llc->dev = NULL;
+	}
 	return rc;
 }
 
@@ -408,6 +412,10 @@ static int llc_ui_bind(struct socket *sock, struct sockaddr *uaddr, int addrlen)
 out_put:
 	llc_sap_put(sap);
 out:
+	if (rc) {
+		dev_put_track(llc->dev, &llc->dev_tracker);
+		llc->dev = NULL;
+	}
 	release_sock(sk);
 	return rc;
 }
-- 
2.35.1.894.gb6a874cedc-goog