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Date:   Thu, 6 Jun 2019 09:55:55 -0700
From:   Guenter Roeck <linux@roeck-us.net>
To:     Eduardo Valentin <eduval@amazon.com>
Cc:     Jean Delvare <jdelvare@suse.com>, linux-hwmon@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCHv2 2/2] hwmon: core: fix potential memory leak in
 *hwmon_device_register*
Message-ID: <20190606165555.GA32130@roeck-us.net>
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On Thu, Jun 06, 2019 at 07:35:44AM -0700, Eduardo Valentin wrote:
> On Wed, Jun 05, 2019 at 01:38:38PM -0700, Guenter Roeck wrote:
> > On Wed, May 29, 2019 at 07:56:05PM -0700, Eduardo Valentin wrote:
> > > When registering a hwmon device with HWMON_C_REGISTER_TZ flag
> > > in place, the hwmon subsystem will attempt to register the device
> > > also with the thermal subsystem. When the of-thermal registration
> > > fails, __hwmon_device_register jumps to ida_remove, leaving
> > > the locally allocated hwdev pointer.
> > > 
> > > This patch fixes the leak by jumping to a new label that
> > > will first unregister hdev and then fall into the kfree of hwdev
> > > to finally remove the idas and propagate the error code.
> > > 
> > 
> > Hah, actually this is wrong. hwdev is freed indirectly with the
> > device_unregister() call. See commit 74e3512731bd ("hwmon: (core)
> > Fix double-free in __hwmon_device_register()").
> 
> heh.. I see it now. Well, it is not a straight catch though. 
> 
> > 
> > It may make sense to add a respective comment to the code, though.
> > 
> 
> I agree. Or a simple comment saying "dont worry about freeing hwdev
> because hwmon_dev_release() takes care of it".
> 
> Are you patching it ?
> 

Will do. I'll send a patch in a minute.

Thanks,
Guenter