linux-kernel - Re: [PATCH] leds: lp50xx: Fix an error handling path in 'lp50xx_probe

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Message-ID: <20200924064932.GP18329@kadam>
Date:   Thu, 24 Sep 2020 09:49:32 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>, pavel@....cz,
        dmurphy@...com, jacek.anaszewski@...il.com,
        linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] leds: lp50xx: Fix an error handling path in
 'lp50xx_probe_dt()'

On Wed, Sep 23, 2020 at 08:49:56PM +0200, Christophe JAILLET wrote:
> Le 23/09/2020 à 15:35, Dan Carpenter a écrit :
> > I've added Heikki Krogerus to the CC list because my question is mostly
> > about commit 59abd83672f7 ("drivers: base: Introducing software nodes to
> > the firmware node framework").
> > 
> > I have been trying to teach Smatch to understand reference counting so
> > it can discover these kinds of bugs automatically.
> > 
> > I don't know how software_node_get_next_child() can work when it doesn't
> > call kobject_get().  This sort of bug would have been caught in testing
> > because it affects the success path so I must be reading the code wrong.
> > 
> 
> I had the same reading of the code and thought that I was missing something
> somewhere.
> 
> There is the same question about 'acpi_get_next_subnode' which is also a
> '.get_next_child_node' function, without any ref counting, if I'm correct.
> 

Yeah, but there aren't any ->get/put() ops for the acpi_get_next_subnode()
stuff so it's not a problem.  (Presumably there is some other sort of
refcounting policy there).

regards,
dan carpenter