Re: [PATCH] nbd: Fix NULL pointer in flush_workqueue

[Sun Ke]

hi，Markus

在 2021/1/29 3:42, Markus Elfring 写道:
> …
> > +++ b/drivers/block/nbd.c
> > @@ -2011,12 +2011,20 @@ static int nbd_genl_disconnect(struct sk_buff *skb, struct genl_info *info)
> >   		       index);
> >   		return -EINVAL;
> >   	}
> > +	mutex_lock(&nbd->config_lock);
> >   	if (!refcount_inc_not_zero(&nbd->refs)) {
> >   		mutex_unlock(&nbd_index_mutex);
> > +		mutex_unlock(&nbd->config_lock);
> Can an other function call order become relevant for the unlocking of these mutexes?
Do you think the nbd->config_lock  mutex here is useless?
> >   		printk(KERN_ERR "nbd: device at index %d is going down\n",
> >   		       index);
> May such an error message be moved into the lock scope?
Sure.
> >   		return -EINVAL;
> >   	}
> > +	if (!nbd->recv_workq) {
> > +		mutex_unlock(&nbd->config_lock);
> > +		mutex_unlock(&nbd_index_mutex);
> > +		return -EINVAL;
> > +	}
> How do you think about to connect the code from this if branch
> with a jump target like “unlock” so that such statements would be shareable
> for the desired exception handling?
OK, I will improve it in V2 patch.
> > +	mutex_unlock(&nbd->config_lock);
> >   	mutex_unlock(&nbd_index_mutex);
> >   	if (!refcount_inc_not_zero(&nbd->config_refs)) {
> >   		nbd_put(nbd);
>
> Regards,
> Markus
> .