net-sysfs: Call dev_hold always in rx_queue_add_kobject

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@syzkaller.appspotmail.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: Jouni Hogander <jouni.hogander@unikie.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 5c4624298996c21607647599a2a07d6cfc3d8ebb..4c826b8bf9b1e18e2cf0f74ebb111022fe1d193f 100644 (file)
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -919,14 +919,17 @@ static int rx_queue_add_kobject(struct net_device *dev, int index)
        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 = dev->queues_kset;
        error = kobject_init_and_add(kobj, &rx_queue_ktype, NULL,
                                     "rx-%u", index);
        if (error)
                goto err;
 
-       dev_hold(queue->dev);
-
        if (dev->sysfs_rx_queue_group) {
                error = sysfs_create_group(kobj, dev->sysfs_rx_queue_group);
                if (error)