linux-kernel - Re: [PATCH v3 3/6] virtio: allow finalize

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Date:	Tue, 9 Dec 2014 14:07:54 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Cornelia Huck <cornelia.huck@...ibm.com>
Cc:	linux-kernel@...r.kernel.org, dahi@...ux.vnet.ibm.com,
	rusty@...tcorp.com.au, Ohad Ben-Cohen <ohad@...ery.com>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	linux390@...ibm.com, Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Sudeep Dutt <sudeep.dutt@...el.com>,
	Siva Yerramreddy <yshivakrishna@...il.com>,
	lguest@...ts.ozlabs.org, linux-s390@...r.kernel.org,
	virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v3 3/6] virtio: allow finalize_features to fail

On Tue, Dec 09, 2014 at 11:46:59AM +0100, Cornelia Huck wrote:
> On Mon, 8 Dec 2014 15:05:58 +0200
> "Michael S. Tsirkin" <mst@...hat.com> wrote:
> 
> > This will make it easy for transports to validate features and return
> > failure.
> > 
> > Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> > ---
> >  include/linux/virtio_config.h          |  3 ++-
> >  drivers/lguest/lguest_device.c         |  4 +++-
> >  drivers/misc/mic/card/mic_virtio.c     |  4 +++-
> >  drivers/remoteproc/remoteproc_virtio.c |  4 +++-
> >  drivers/s390/kvm/kvm_virtio.c          |  4 +++-
> >  drivers/s390/kvm/virtio_ccw.c          |  6 ++++--
> >  drivers/virtio/virtio.c                | 21 ++++++++++++++-------
> >  drivers/virtio/virtio_mmio.c           |  4 +++-
> >  drivers/virtio/virtio_pci.c            |  4 +++-
> >  9 files changed, 38 insertions(+), 16 deletions(-)
> > 
> 
> > diff --git a/drivers/s390/kvm/virtio_ccw.c b/drivers/s390/kvm/virtio_ccw.c
> > index c792b5f..789275f 100644
> > --- a/drivers/s390/kvm/virtio_ccw.c
> > +++ b/drivers/s390/kvm/virtio_ccw.c
> > @@ -752,7 +752,7 @@ out_free:
> >  	return rc;
> >  }
> > 
> > -static void virtio_ccw_finalize_features(struct virtio_device *vdev)
> > +static int virtio_ccw_finalize_features(struct virtio_device *vdev)
> >  {
> >  	struct virtio_ccw_device *vcdev = to_vc_device(vdev);
> >  	struct virtio_feature_desc *features;
> > @@ -760,7 +760,7 @@ static void virtio_ccw_finalize_features(struct virtio_device *vdev)
> > 
> >  	ccw = kzalloc(sizeof(*ccw), GFP_DMA | GFP_KERNEL);
> >  	if (!ccw)
> > -		return;
> > +		return 0;
> 
> I think we'll want to return an error in this case as well to fail
> probing. Also for the other places where something can go wrong.
> Something like this:


I guess the fact this previously failed silently is a bug in original
code?

Can you please send your S.O.B so I can add this patch on top?

We might also need to Cc stable.


> diff --git a/drivers/s390/kvm/virtio_ccw.c b/drivers/s390/kvm/virtio_ccw.c
> index 789275f..bc6e671 100644
> --- a/drivers/s390/kvm/virtio_ccw.c
> +++ b/drivers/s390/kvm/virtio_ccw.c
> @@ -757,15 +757,17 @@ static int virtio_ccw_finalize_features(struct virtio_device *vdev)
>  	struct virtio_ccw_device *vcdev = to_vc_device(vdev);
>  	struct virtio_feature_desc *features;
>  	struct ccw1 *ccw;
> +	int ret;
>  
>  	ccw = kzalloc(sizeof(*ccw), GFP_DMA | GFP_KERNEL);
>  	if (!ccw)
> -		return 0;
> +		return -ENOMEM;
>  
>  	features = kzalloc(sizeof(*features), GFP_DMA | GFP_KERNEL);
> -	if (!features)
> +	if (!features) {
> +		ret = -ENOMEM;
>  		goto out_free;
> -
> +	}
>  	/* Give virtio_ring a chance to accept features. */
>  	vring_transport_features(vdev);
>  
> @@ -776,7 +778,9 @@ static int virtio_ccw_finalize_features(struct virtio_device *vdev)
>  	ccw->flags = 0;
>  	ccw->count = sizeof(*features);
>  	ccw->cda = (__u32)(unsigned long)features;
> -	ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_WRITE_FEAT);
> +	ret = ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_WRITE_FEAT);
> +	if (ret)
> +		goto out_free;
>  
>  	if (vcdev->revision == 0)
>  		goto out_free;
> @@ -788,13 +792,13 @@ static int virtio_ccw_finalize_features(struct virtio_device *vdev)
>  	ccw->flags = 0;
>  	ccw->count = sizeof(*features);
>  	ccw->cda = (__u32)(unsigned long)features;
> -	ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_WRITE_FEAT);
> +	ret = ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_WRITE_FEAT);
>  
>  out_free:
>  	kfree(features);
>  	kfree(ccw);
>  
> -	return 0;
> +	return ret;
>  }
>  
>  static void virtio_ccw_get_config(struct virtio_device *vdev,
--
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