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SubjectRe: [PATCH net 3/3] netdevsim: psp: rcu protect psp_dev reference
Daniel Zahka wrote:
>
> On 5/6/26 3:34 PM, Willem de Bruijn wrote:
> > Daniel Zahka wrote
> >> static ssize_t
> >> @@ -228,16 +237,23 @@ nsim_psp_rereg_write(struct file *file, const char __user *data, size_t count,
> >> loff_t *ppos)
> >> {
> >> struct netdevsim *ns = file->private_data;
> >> - int err;
> >> + struct psp_dev *psd;
> >> + ssize_t ret;
> >>
> >> mutex_lock(&ns->psp.rereg_lock);
> >> - __nsim_psp_uninit(ns);
> >> + __nsim_psp_uninit(ns, false);
> >> +
> >> + psd = psp_dev_create(ns->netdev, &nsim_psp_ops, &nsim_psp_caps, ns);
> >> + if (IS_ERR(psd)) {
> >> + ret = PTR_ERR(psd);
> >> + goto out;
> >> + }
> > Do you want to create the new device first and only delete the old
> > state if that succeeds? To avoid a netdevsim in state without dev.
> >
> >>
> >> - ns->psp.dev = psp_dev_create(ns->netdev, &nsim_psp_ops,
> >> - &nsim_psp_caps, ns);
> >> - err = PTR_ERR_OR_ZERO(ns->psp.dev);
> >> + rcu_assign_pointer(ns->psp.dev, psd);
> >> + ret = count;
> >> +out:
> >> mutex_unlock(&ns->psp.rereg_lock);
> >> - return err ?: count;
> >> + return ret;
> >> }
> >>
>
> Unfortunately, the way we have psp_dev_unregister() written, it would
> clear out the main_netdev->psp_dev field from the second
> psp_dev_create() call. I don't believe there is use case to do this in a
> real driver, so I'm not sure we need to change how the create/unregister
> paths work.

Thanks for that context.

Reviewed-by: Willem de Bruijn <willemb@google.com>



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