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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, Hulk Robot <hulkci@huawei.com>,
        Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
        David Miller <davem@davemloft.net>,
        Lukas Bulwahn <lukas.bulwahn@gmail.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.4 099/102] net-sysfs: Call dev_hold always in netdev_queue_add_kobject
Date:   Fri, 24 Jan 2020 10:31:40 +0100
Message-Id: <20200124092821.671503824@linuxfoundation.org>
In-Reply-To: <20200124092806.004582306@linuxfoundation.org>
References: <20200124092806.004582306@linuxfoundation.org>
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From: Jouni Hogander <jouni.hogander@unikie.com>

[ Upstream commit e0b60903b434a7ee21ba8d8659f207ed84101e89 ]

Dev_hold has to be called always in netdev_queue_add_kobject.
Otherwise usage count drops below 0 in case of failure in
kobject_init_and_add.

Fixes: b8eb718348b8 ("net-sysfs: Fix reference count leak in rx|netdev_queue_add_kobject")
Reported-by: Hulk Robot <hulkci@huawei.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: David Miller <davem@davemloft.net>
Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/core/net-sysfs.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index b4db68e5caa9a..4c826b8bf9b1e 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -1462,14 +1462,17 @@ static int netdev_queue_add_kobject(struct net_device *dev, int index)
 	struct kobject *kobj = &queue->kobj;
 	int error = 0;
 
+	/* Kobject_put later will trigger netdev_queue_release call
+	 * which decreases dev refcount: Take that reference here
+	 */
+	dev_hold(queue->dev);
+
 	kobj->kset = dev->queues_kset;
 	error = kobject_init_and_add(kobj, &netdev_queue_ktype, NULL,
 				     "tx-%u", index);
 	if (error)
 		goto err;
 
-	dev_hold(queue->dev);
-
 #ifdef CONFIG_BQL
 	error = sysfs_create_group(kobj, &dql_group);
 	if (error)
-- 
2.20.1