linux-kernel - RE: [PATCH v10 13/15] platform/x86: wmi: create userspace interface for drivers

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Date:   Fri, 20 Oct 2017 13:54:36 +0000
From:   <Mario.Limonciello@...l.com>
To:     <greg@...ah.com>
CC:     <dvhart@...radead.org>, <andy.shevchenko@...il.com>,
        <linux-kernel@...r.kernel.org>,
        <platform-driver-x86@...r.kernel.org>, <luto@...nel.org>,
        <quasisec@...gle.com>, <pali.rohar@...il.com>, <rjw@...ysocki.net>,
        <mjg59@...gle.com>, <hch@....de>, <gnomes@...rguk.ukuu.org.uk>
Subject: RE: [PATCH v10 13/15] platform/x86: wmi: create userspace interface
 for drivers

> -----Original Message-----
> From: Greg KH [mailto:greg@...ah.com]
> Sent: Friday, October 20, 2017 8:22 AM
> To: Limonciello, Mario <Mario_Limonciello@...l.com>
> Cc: dvhart@...radead.org; Andy Shevchenko <andy.shevchenko@...il.com>;
> LKML <linux-kernel@...r.kernel.org>; platform-driver-x86@...r.kernel.org; Andy
> Lutomirski <luto@...nel.org>; quasisec@...gle.com; pali.rohar@...il.com;
> rjw@...ysocki.net; mjg59@...gle.com; hch@....de; Alan Cox
> <gnomes@...rguk.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.

> > +	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.