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

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Date: Tue, 23 Apr 2024 16:00:25 +0800
From: David Gow <davidgow@...gle.com>
To: Wander Lairson Costa <wander@...hat.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Brendan Higgins <brendan.higgins@...ux.dev>, 
	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, 19 Apr 2024 at 22:11, Wander Lairson Costa <wander@...hat.com> wrote:
>
> 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. Don't worry about sending a v5: just patch 1 of v4 is now in
the kunit branch:
https://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest.git/commit/?h=kunit&id=63761ec5971ea47c1f2d7698f03e1c6ffb9fb22a

Cheers,
-- David

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