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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Eric Dumazet <edumazet@google.com>,
        =?UTF-8?q?=E8=B5=B5=E5=AD=90=E8=BD=A9?= <beraphin@gmail.com>,
        Stoyan Manolov <smanolov@suse.de>,
        Jakub Kicinski <kuba@kernel.org>
Subject: [PATCH 4.19 06/20] llc: fix netdevice reference leaks in llc_ui_bind()
Date:   Fri, 25 Mar 2022 16:04:44 +0100
Message-Id: <20220325150417.195021457@linuxfoundation.org>
In-Reply-To: <20220325150417.010265747@linuxfoundation.org>
References: <20220325150417.010265747@linuxfoundation.org>
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From: Eric Dumazet <edumazet@google.com>

commit 764f4eb6846f5475f1244767d24d25dd86528a4a upstream.

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@google.com>
Reported-by: 赵子轩 <beraphin@gmail.com>
Reported-by: Stoyan Manolov <smanolov@suse.de>
Link: https://lore.kernel.org/r/20220323004147.1990845-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/llc/af_llc.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/net/llc/af_llc.c
+++ b/net/llc/af_llc.c
@@ -311,6 +311,10 @@ static int llc_ui_autobind(struct socket
 	sock_reset_flag(sk, SOCK_ZAPPED);
 	rc = 0;
 out:
+	if (rc) {
+		dev_put(llc->dev);
+		llc->dev = NULL;
+	}
 	return rc;
 }
 
@@ -410,6 +414,10 @@ static int llc_ui_bind(struct socket *so
 out_put:
 	llc_sap_put(sap);
 out:
+	if (rc) {
+		dev_put(llc->dev);
+		llc->dev = NULL;
+	}
 	release_sock(sk);
 	return rc;
 }