[PATCH 3.16 10/61] net-sysfs: Call dev_hold always in rx_queue_add_kobject

[Ben Hutchings]

3.16.85-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Jouni Hogander <jouni.hogander@xxxxxxxxxx>

commit ddd9b5e3e765d8ed5a35786a6cb00111713fe161 upstream.

Dev_hold has to be called always in rx_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: syzbot <syzbot+30209ea299c09d8785c9@xxxxxxxxxxxxxxxxxxxxxxxxx>
Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Cc: David Miller <davem@xxxxxxxxxxxxx>
Cc: Lukas Bulwahn <lukas.bulwahn@xxxxxxxxx>
Signed-off-by: Jouni Hogander <jouni.hogander@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 net/core/net-sysfs.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -782,14 +782,17 @@ static int rx_queue_add_kobject(struct n
 	struct kobject *kobj = &queue->kobj;
 	int error = 0;
 
+	/* Kobject_put later will trigger rx_queue_release call which
+	 * decreases dev refcount: Take that reference here
+	 */
+	dev_hold(queue->dev);
+
 	kobj->kset = net->queues_kset;
 	error = kobject_init_and_add(kobj, &rx_queue_ktype, NULL,
 	    "rx-%u", index);
 	if (error)
 		goto err;
 
-	dev_hold(queue->dev);
-
 	if (net->sysfs_rx_queue_group) {
 		error = sysfs_create_group(kobj, net->sysfs_rx_queue_group);
 		if (error)