Re: [PATCH v3 3/6] virtio: allow finalize_features to fail

[Cornelia Huck <cornelia.huck@de.ibm.com>]

On Tue, 9 Dec 2014 14:07:54 +0200
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> 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@redhat.com> wrote:
> > 
> > > This will make it easy for transports to validate features and return
> > > failure.
> > > 
> > > Signed-off-by: Michael S. Tsirkin <mst@redhat.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?

Not really a bug; it simply was not possible to fail it.

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

Sure. Code below is

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>

> 
> We might also need to Cc stable.

Not sure whether this is stable-worthy, as these are largely
pathological cases (and for the one non-pathological case, device going
away, we're already fine).

> 
> 
> > 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,
>