net-sysfs: call dev_hold if kobject_init_and_add success [Linux 5.1]

net-sysfs: call dev_hold if kobject_init_and_add success [Linux 5.1]

This Linux kernel change "net-sysfs: call dev_hold if kobject_init_and_add success" is included in the Linux 5.1 release. This change is authored by YueHaibing <yuehaibing [at] huawei.com> on Tue Mar 19 10:16:53 2019 +0800. The commit for this change in Linux stable tree is a3e23f7 (patch).

net-sysfs: call dev_hold if kobject_init_and_add success

In netdev_queue_add_kobject and rx_queue_add_kobject,
if sysfs_create_group failed, kobject_put will call
netdev_queue_release to decrease dev refcont, however
dev_hold has not be called. So we will see this while
unregistering dev:

unregister_netdevice: waiting for bcsh0 to become free. Usage count = -1

Reported-by: Hulk Robot <hulkci@huawei.com>
Fixes: d0d668371679 ("net: don't decrement kobj reference count on init failure")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

There are 6 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 net/core/net-sysfs.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 4ff661f..8f8b7b6 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -928,6 +928,8 @@ static int rx_queue_add_kobject(struct net_device *dev, int index)
    if (error)
        return error;

+   dev_hold(queue->dev);
+
    if (dev->sysfs_rx_queue_group) {
        error = sysfs_create_group(kobj, dev->sysfs_rx_queue_group);
        if (error) {
@@ -937,7 +939,6 @@ static int rx_queue_add_kobject(struct net_device *dev, int index)
    }

    kobject_uevent(kobj, KOBJ_ADD);
-   dev_hold(queue->dev);

    return error;
 }
@@ -1464,6 +1465,8 @@ static int netdev_queue_add_kobject(struct net_device *dev, int index)
    if (error)
        return error;

+   dev_hold(queue->dev);
+
 #ifdef CONFIG_BQL
    error = sysfs_create_group(kobj, &dql_group);
    if (error) {
@@ -1473,7 +1476,6 @@ static int netdev_queue_add_kobject(struct net_device *dev, int index)
 #endif

    kobject_uevent(kobj, KOBJ_ADD);
-   dev_hold(queue->dev);

    return 0;
 }

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