Re: [PATCH 3/3] net-sysfs: Fix error path for kobject_init_and_add()

[wanghai (M)]

å 2019/5/1 0:11, Andy Shevchenko åé:
> On Tue, Apr 30, 2019 at 10:28:17AM +1000, Tobin C. Harding wrote:
> > Currently error return from kobject_init_and_add() is not followed by a
> > call to kobject_put().  This means there is a memory leak.
> >
> > Add call to kobject_put() in error path of kobject_init_and_add().
> It's not obvious to me if this will help to fix what is stated in the
> (reverted) commit 6b70fc94afd1 ("net-sysfs: Fix memory leak in
> netdev_register_kobject")?
>
> If so, perhaps we need to tell syzkaller guys about this.
Thanks for reminding. It seems that the bug has not been completely fixed.

in netdev_register_kobject():

1746ÂÂÂÂÂÂÂÂ error = device_add(dev);
1747ÂÂÂÂÂÂÂÂ if (error)
1748ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ return error;
1749
1750ÂÂÂÂÂÂÂÂ error = register_queue_kobjects(ndev);
1751ÂÂÂÂÂÂÂÂ if (error) {
1752ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ device_del(dev);
1753ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ return error;
1754ÂÂÂÂÂÂÂÂ }

This only fixes a memory leak after a failure in 
register_queue_kobjects(). If device_add() fails, kobject_put() still 
cann't be called, and the memory leak still exists.