Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   KY Srinivasan <kys@microsoft.com>
To:     "Michael Kelley (EOSG)" <Michael.H.Kelley@microsoft.com>,
        Arvind Yadav <arvind.yadav.cs@gmail.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>
CC:     "devel@linuxdriverproject.org" <devel@linuxdriverproject.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] vmbus: use put_device() if device_register fail
Thread-Topic: [PATCH] vmbus: use put_device() if device_register fail
Thread-Index: AQHTvoUaSaPHx26coEaurL53qMiDJaPW37dwgAALLICAACFeAA==
Date:   Mon, 19 Mar 2018 05:52:16 +0000
Message-ID: <DM5PR2101MB0888249051F5FE11B0AE089AA0D40@DM5PR2101MB0888.namprd21.prod.outlook.com>
References: <bd6526dedf570a226ee024907be9a8f2bb04803f.1521355469.git.arvind.yadav.cs@gmail.com>
 <SN6PR2101MB0893ED30DA3AAFD4B3E2064EA0D40@SN6PR2101MB0893.namprd21.prod.outlook.com>
 <DM5PR2101MB103094D4CE169185B16EE0E9DCD40@DM5PR2101MB1030.namprd21.prod.outlook.com>
In-Reply-To: <DM5PR2101MB103094D4CE169185B16EE0E9DCD40@DM5PR2101MB1030.namprd21.prod.outlook.com>
Accept-Language: en-US
Content-Language: en-US
received-spf: None (protection.outlook.com: microsoft.com does not designate
 permitted sender hosts)
spamdiagnosticoutput: 1:99
spamdiagnosticmetadata: NSPM
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-MS-Exchange-CrossTenant-Network-Message-Id: dca5a4ed-5331-473c-ff12-08d58d5d9302
X-MS-Exchange-CrossTenant-originalarrivaltime: 19 Mar 2018 05:52:17.8793
 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR2101MB0981
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org


> -----Original Message-----
> From: Michael Kelley (EOSG)
> Sent: Sunday, March 18, 2018 8:40 PM
> To: KY Srinivasan <kys@microsoft.com>; Arvind Yadav
> <arvind.yadav.cs@gmail.com>; Stephen Hemminger
> <sthemmin@microsoft.com>; Haiyang Zhang <haiyangz@microsoft.com>
> Cc: devel@linuxdriverproject.org; linux-kernel@vger.kernel.org
> Subject: RE: [PATCH] vmbus: use put_device() if device_register fail
>=20
> > -----Original Message-----
> > From: linux-kernel-owner@vger.kernel.org <linux-kernel-
> owner@vger.kernel.org> On Behalf
> > Of KY Srinivasan
> > Sent: Sunday, March 18, 2018 8:02 PM
> > To: Arvind Yadav <arvind.yadav.cs@gmail.com>; Stephen Hemminger
> > <sthemmin@microsoft.com>; Haiyang Zhang <haiyangz@microsoft.com>
> > Cc: devel@linuxdriverproject.org; linux-kernel@vger.kernel.org
> > Subject: RE: [PATCH] vmbus: use put_device() if device_register fail
> >
> > > -----Original Message-----
> > > From: devel <driverdev-devel-bounces@linuxdriverproject.org> On
> Behalf
> > > Of Arvind Yadav
> > > Sent: Saturday, March 17, 2018 11:48 PM
> > > To: Stephen Hemminger <sthemmin@microsoft.com>; Haiyang Zhang
> > > <haiyangz@microsoft.com>
> > > Cc: devel@linuxdriverproject.org; linux-kernel@vger.kernel.org
> > > Subject: [PATCH] vmbus: use put_device() if device_register fail
> > >
> > > if device_register() returned an error. Always use put_device()
> > > to give up the reference initialized.
> > >
> > > Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
> > > ---
> > >  drivers/hv/vmbus_drv.c | 1 +
> > >  1 file changed, 1 insertion(+)
> > >
> > > diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> > > index bc65c4d..25da2f3 100644
> > > --- a/drivers/hv/vmbus_drv.c
> > > +++ b/drivers/hv/vmbus_drv.c
> > > @@ -1358,6 +1358,7 @@ int vmbus_device_register(struct hv_device
> > > *child_device_obj)
> > >  	ret =3D device_register(&child_device_obj->device);
> > >  	if (ret) {
> > >  		pr_err("Unable to register child device\n");
> > > +		put_device(&child_device_obj->device);
> >
> > If the registration failed; we would not have acquired the reference on=
 the
> device and so
> > we should not be dropping the reference in the failure path.
>=20
> Looking at the code for device_register() and its constituent parts
> device_initialize() and device_add(), Arvind is correct.  device_initiali=
ze()
> creates the object with a reference count of 1.  device_add() does not
> decrement that reference count or free the object, even if it fails.  The
> comments for device_register() call this out as well.

Yes; agreed. I will take this patch.

K. Y
>=20
> Michael
>=20
> >
> > K. Y
> > >  		return ret;
> > >  	}
> > >
> > > --
> > > 2.7.4