netdev - RE: [PATCH 2/4] mdev: Make mdev alias unique among all mdevs

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Date:   Tue, 27 Aug 2019 04:28:37 +0000
From:   Parav Pandit <parav@...lanox.com>
To:     Mark Bloch <markb@...lanox.com>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        Jiri Pirko <jiri@...lanox.com>,
        "kwankhede@...dia.com" <kwankhede@...dia.com>,
        "cohuck@...hat.com" <cohuck@...hat.com>,
        "davem@...emloft.net" <davem@...emloft.net>
CC:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH 2/4] mdev: Make mdev alias unique among all mdevs

Hi Mark,

> -----Original Message-----
> From: Mark Bloch <markb@...lanox.com>
> Sent: Tuesday, August 27, 2019 4:32 AM
> To: Parav Pandit <parav@...lanox.com>; alex.williamson@...hat.com; Jiri
> Pirko <jiri@...lanox.com>; kwankhede@...dia.com; cohuck@...hat.com;
> davem@...emloft.net
> Cc: kvm@...r.kernel.org; linux-kernel@...r.kernel.org;
> netdev@...r.kernel.org
> Subject: Re: [PATCH 2/4] mdev: Make mdev alias unique among all mdevs
> 
> 
> 
> On 8/26/19 1:41 PM, Parav Pandit wrote:
> > Mdev alias should be unique among all the mdevs, so that when such
> > alias is used by the mdev users to derive other objects, there is no
> > collision in a given system.
> >
> > Signed-off-by: Parav Pandit <parav@...lanox.com>
> > ---
> >  drivers/vfio/mdev/mdev_core.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/drivers/vfio/mdev/mdev_core.c
> > b/drivers/vfio/mdev/mdev_core.c index e825ff38b037..6eb37f0c6369
> > 100644
> > --- a/drivers/vfio/mdev/mdev_core.c
> > +++ b/drivers/vfio/mdev/mdev_core.c
> > @@ -375,6 +375,11 @@ int mdev_device_create(struct kobject *kobj,
> struct device *dev,
> >  			ret = -EEXIST;
> >  			goto mdev_fail;
> >  		}
> > +		if (tmp->alias && strcmp(tmp->alias, alias) == 0) {
> 
> alias can be NULL here no?
> 
If alias is NULL, tmp->alias would also be null because for given parent either we have alias or we don’t.
So its not possible to have tmp->alias as null and alias as non null.
But it may be good/defensive to add check for both.

> > +			mutex_unlock(&mdev_list_lock);
> > +			ret = -EEXIST;
> > +			goto mdev_fail;
> > +		}
> >  	}
> >
> >  	mdev = kzalloc(sizeof(*mdev), GFP_KERNEL);
> >
> 
> Mark