Re: [PATCH v4 07/18] nitro_enclaves: Init misc device providing the ioctl interface

[Paraschiv, Andra-Irina]

On 30/06/2020 11:05, Greg KH wrote:
> On Mon, Jun 29, 2020 at 08:45:25PM +0300, Paraschiv, Andra-Irina wrote:
> > On 29/06/2020 19:20, Greg KH wrote:
> > > On Mon, Jun 22, 2020 at 11:03:18PM +0300, Andra Paraschiv wrote:
> > > > +static int __init ne_init(void)
> > > > +{
> > > > +     struct pci_dev *pdev = pci_get_device(PCI_VENDOR_ID_AMAZON,
> > > > +                                           PCI_DEVICE_ID_NE, NULL);
> > > > +     int rc = -EINVAL;
> > > > +
> > > > +     if (!pdev)
> > > > +             return -ENODEV;
> > > Ick, that's a _very_ old-school way of binding to a pci device.  Please
> > > just be a "real" pci driver and your probe function will be called if
> > > your hardware is present (or when it shows up.)  To do it this way
> > > prevents your driver from being auto-loaded for when your hardware is
> > > seen in the system, as well as lots of other things.
> > This check is mainly here in the case any codebase is added before the pci
> > driver register call below.
> What do you mean by "codebase"?  You control this driver, just do all of
> the logic in the probe() function, no need to do this in the module init
> call.
>
> > And if we log any error with dev_err() instead of pr_err() before the driver
> > register.
> Don't do that.
>
> > That check was only for logging purposes, if done with dev_err(). I removed
> > the check in v5.
> Again, don't do it :)
>
> > > > +
> > > > +     if (!zalloc_cpumask_var(&ne_cpu_pool.avail, GFP_KERNEL))
> > > > +             return -ENOMEM;
> > > > +
> > > > +     mutex_init(&ne_cpu_pool.mutex);
> > > > +
> > > > +     rc = pci_register_driver(&ne_pci_driver);
> > > Nice, you did it right here, but why the above crazy test?
> > >
> > > > +     if (rc < 0) {
> > > > +             dev_err(&pdev->dev,
> > > > +                     "Error in pci register driver [rc=%d]\n", rc);
> > > > +
> > > > +             goto free_cpumask;
> > > > +     }
> > > > +
> > > > +     return 0;
> > > You leaked a reference on that pci device, didn't you?  Not good :(
> > Yes, the pci get device call needs its pair - pci_dev_put(). I added it here
> > and for the other occurrences where it was missing.
> Again, just don't do it and then you don't have to worry about any of
> this.

Yup, already started this morning to check & update where we can go 
without this call to get a PCI device reference, as a follow-up to what 
we discussed yesterday.

Thanks,
Andra



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