RE: [PATCH v3 net] net: enetc: fix VSI mailbox timeout handling and DMA lifecycle

[Wei Fang]

> > @@ -259,6 +282,7 @@ static void enetc_vf_remove(struct pci_dev *pdev)
> > {
> >  	struct enetc_si *si = pci_get_drvdata(pdev);
> >  	struct enetc_ndev_priv *priv;
> > +	struct enetc_msg_swbd msg;
> >
> >  	priv = netdev_priv(si->ndev);
> >  	unregister_netdev(si->ndev);
> > @@ -270,7 +294,9 @@ static void enetc_vf_remove(struct pci_dev *pdev)
> >
> >  	free_netdev(si->ndev);
> >
> > +	msg = si->msg;
> >  	enetc_pci_remove(pdev);
> > +	enetc_msg_dma_free(&pdev->dev, &msg);
> 
> Is it possible for the mailbox to still be busy here?
> 
> The commit addresses the use-after-free in the send path by checking the
> mailbox busy status before freeing the previous buffer. However, during driver
> teardown, enetc_msg_dma_free() is called unconditionally.
> 
> If a prior message sent via enetc_msg_vsi_send() times out and the hardware is
> still accessing the buffer, and then the driver is unbound, could this cause the
> hardware to read from freed DMA memory?
> 
> Should the teardown path wait for the mailbox to become idle or ensure the
> hardware is safely reset before freeing the buffer?
> 

enetc_msg_dma_free() is called after enetc_pci_remove(), enetc_pci_remove()
will disable the device, so it is safe to free the buffer.