linux-kernel - Re: [PATCH v4 2/2] kunit: avoid memory leak on device register error

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Message-ID: <CAAq0SUnjc03N5kHgJ8vwk19BjzQr8DCRCokh09npmCs2mxxwXA@mail.gmail.com>
Date: Fri, 19 Apr 2024 11:11:29 -0300
From: Wander Lairson Costa <wander@...hat.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Brendan Higgins <brendan.higgins@...ux.dev>, David Gow <davidgow@...gle.com>, 
	Rae Moar <rmoar@...gle.com>, Shuah Khan <skhan@...uxfoundation.org>, 
	Matti Vaittinen <mazziesaccount@...il.com>, Maxime Ripard <mripard@...nel.org>, 
	"open list:KERNEL UNIT TESTING FRAMEWORK (KUnit)" <linux-kselftest@...r.kernel.org>, 
	"open list:KERNEL UNIT TESTING FRAMEWORK (KUnit)" <kunit-dev@...glegroups.com>, open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 2/2] kunit: avoid memory leak on device register error

On Fri, Apr 19, 2024 at 11:03 AM Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
>
> On Fri, Apr 19, 2024 at 10:25:02AM -0300, Wander Lairson Costa wrote:
> > If the device register fails, free the allocated memory before
> > returning.
> >
> > Signed-off-by: Wander Lairson Costa <wander@...hat.com>
> > Fixes: d03c720e03bd ("kunit: Add APIs for managing devices")
> > ---
> >  lib/kunit/device.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/lib/kunit/device.c b/lib/kunit/device.c
> > index 25c81ed465fb..d8c09dcb3e79 100644
> > --- a/lib/kunit/device.c
> > +++ b/lib/kunit/device.c
> > @@ -131,6 +131,7 @@ static struct kunit_device *kunit_device_register_internal(struct kunit *test,
> >       err = device_register(&kunit_dev->dev);
> >       if (err) {
> >               put_device(&kunit_dev->dev);
> > +             kfree(kunit_dev);
>
> This still looks wrong, the release function for the device should free
> the memory here, not this kfree, as the reference count in the embedded
> 'struct device' handles the memory logic for the whole structure (if
> not, then something is REALLY wrong...)
>
> You _do_ have a release function for the device, right?  If not, you
> should be getting loud messages in the kernel log when releasing a
> device here.
>

Ok, I got it. Yes, there is a release function. So this patch is
wrong, ignore it. Should I send a v5 with only the other patch?

> thanks,
>
> greg k-h
>