[PATCH] net-sysfs: Call dev_hold always in netdev_queue_add_kobject

[PATCH] net-sysfs: Call dev_hold always in netdev_queue_add_kobject

[jouni.hogander]

From: Jouni Hogander <jouni.hogander@unikie.com>

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>
---
 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 ae3bcb1540ec..5c4624298996 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -1459,14 +1459,17 @@ 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)
-- 
2.17.1

Re: [PATCH] net-sysfs: Call dev_hold always in netdev_queue_add_kobject

[David Miller]

From: jouni.hogander@unikie.com
Date: Thu,  5 Dec 2019 15:57:07 +0200

> From: Jouni Hogander <jouni.hogander@unikie.com>
> 
> 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>

Applied and queued up for -stable, thanks.