On Fri, Oct 20, 2017 at 01:54:36PM +0000, Mario.Limonciello@xxxxxxxx wrote: > > -----Original Message----- > > From: Greg KH [mailto:greg@xxxxxxxxx] > > Sent: Friday, October 20, 2017 8:22 AM > > To: Limonciello, Mario <Mario_Limonciello@xxxxxxxx> > > Cc: dvhart@xxxxxxxxxxxxx; Andy Shevchenko <andy.shevchenko@xxxxxxxxx>; > > LKML <linux-kernel@xxxxxxxxxxxxxxx>; platform-driver-x86@xxxxxxxxxxxxxxx; Andy > > Lutomirski <luto@xxxxxxxxxx>; quasisec@xxxxxxxxxx; pali.rohar@xxxxxxxxx; > > rjw@xxxxxxxxxxxxx; mjg59@xxxxxxxxxx; hch@xxxxxx; Alan Cox > > <gnomes@xxxxxxxxxxxxxxxxxxx> > > 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. container_of can never return NULL, it does arithmetics on a pointer based on the type it is embedded into. You better don't register a wmi_device that's not part of the block with your driver. Which others drivers are those, btw? > > > + 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. See above, no it can't. Maybe wblock->dev.dev.driver can be NULL, but in that case you must not call container_of on it.
