linux-kernel - Re: v5.13-rcX regression - NULL pointer dereference

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Date:   Tue, 22 Jun 2021 17:10:44 +0300
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     Dominik Brodowski <linux@...inikbrodowski.net>
Cc:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Lee Jones <lee.jones@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: v5.13-rcX regression - NULL pointer dereference - MFD and
 software node API

On Tue, Jun 22, 2021 at 11:09:58AM +0300, Heikki Krogerus wrote:
> On Mon, Jun 21, 2021 at 05:31:50PM +0200, Dominik Brodowski wrote:
> > Am Mon, Jun 21, 2021 at 01:37:59PM +0300 schrieb Heikki Krogerus:
> > > On Mon, Jun 21, 2021 at 01:00:06PM +0300, Andy Shevchenko wrote:
> > > > Can you, please, attach this to the bug report?
> > > > 
> > > > Long story here is that the device creation fails but we already have added
> > > > swnode to it. Meanwhile, device itself is not completely instantiated (yet)
> > > > and dev_name(dev) is NULL. The software_node_notify() is called with such
> > > > device and Oopses in the following line
> > > > 
> > > > 	sysfs_remove_link(&swnode->kobj, dev_name(dev));
> > > > 
> > > > My patch fixes another issue that might happen before this and in the code
> > > > that retrieves swnode itself in the device_remove_software_node().
> > > > 
> > > > Of course my patch won't fix this issue.
> > > > 
> > > > I have heard that Heikki is looking how to fix the issue in your case and
> > > > potentially in any other cases where device_add_software_node() is called
> > > > against not formed object instance.
> > > 
> > > Dominik, can you test the attached patch to confirm if this really is
> > > the case.
> > 
> > With this patch applied, the panic disappears.
> 
> Thanks Dominik. I'll clean it and send it out today.

Before I send the patch to Rafael and Greg, can you confirm that the
appropriate API (device_is_registered()) also works? I'm attaching
patch that should be the final version (if it works).

I'm sorry to bother you with this.

thanks,

-- 
heikki

View attachment "0001-software-node-Handle-software-node-injection-to-an-e.patch" of type "text/plain" (2244 bytes)