On Fri, Oct 20, 2017 at 01:54:36PM +0000, mario.limoncie...@dell.com wrote:
> > -----Original Message-----
> > From: Greg KH [mailto:g...@kroah.com]
> > Sent: Friday, October 20, 2017 8:22 AM
> > To: Limonciello, Mario <mario_limoncie...@dell.com>
> > Cc: dvh...@infradead.org; Andy Shevchenko <andy.shevche...@gmail.com>;
> > LKML <linux-kernel@vger.kernel.org>; platform-driver-...@vger.kernel.org;
> > Andy
> > Lutomirski <l...@kernel.org>; quasi...@google.com; pali.ro...@gmail.com;
> > r...@rjwysocki.net; mj...@google.com; h...@lst.de; Alan Cox
> > <gno...@lxorguk.ukuu.org.uk>
> > Subject: Re: [PATCH v10 13/15] platform/x86: wmi: create userspace
> > interface for
> > drivers
> >
> > On Thu, Oct 19, 2017 at 12:50:16PM -0500, Mario Limonciello wrote:
> > > + wblock = container_of(wdev, struct wmi_block, dev);
> > > + if (!wblock)
> > > + return -ENODEV;
> >
> > How can container_of() ever return NULL? If so, you have a very odd
> > memory layout...
> >
>
> I'm assuming this is from set_required_buffer_size right?
>
> The symbol is exported out for other drivers to use. It's possible for
> another
> driver to allocate a wmi_device structure that's not part of a wblock.
Fine, but your test does not do anything at all.
> > > + list_for_each_entry_safe(wblock, next, &wmi_block_list, list) {
> > > + wdriver = container_of(wblock->dev.dev.driver,
> > > + struct wmi_driver, driver);
> > > + if (!wdriver)
> > > + continue;
> >
> > Same here. And other places in this file.
> >
>
> This one it's possible that a driver isn't bound to a device, and when
> that happens wdriver is NULL.
Again, that's not what you are testing at all.
container_of() is just pointer math. If you pass in NULL, you will get
a non-NULL value (incremented or decremented). If you pass in a very
tiny number, you might get NULL, but that's still really wrong.
In other words, these tests will _NEVER_ fail. Go ahead, try it :)
thanks,
greg k-h
