Re: [PATCH v14 30/42] virtio_pci: introduce helper to get/set queue reset

[Xuan Zhuo <xuanzhuo@linux.alibaba.com>]

On Fri, 22 Sep 2023 06:46:39 -0400, "Michael S. Tsirkin" <mst@redhat.com> wrote:
> On Fri, Sep 22, 2023 at 09:49:18AM +0800, Xuan Zhuo wrote:
> > On Thu, 21 Sep 2023 10:02:53 -0400, "Michael S. Tsirkin" <mst@redhat.com> wrote:
> > > On Mon, Aug 01, 2022 at 02:38:50PM +0800, Xuan Zhuo wrote:
> > > > Introduce new helpers to implement queue reset and get queue reset
> > > > status.
> > > >
> > > >  https://github.com/oasis-tcs/virtio-spec/issues/124
> > > >  https://github.com/oasis-tcs/virtio-spec/issues/139
> > > >
> > > > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> > > > Acked-by: Jason Wang <jasowang@redhat.com>
> > > > ---
> > > >  drivers/virtio/virtio_pci_modern_dev.c | 39 ++++++++++++++++++++++++++
> > > >  include/linux/virtio_pci_modern.h      |  2 ++
> > > >  2 files changed, 41 insertions(+)
> > > >
> > > > diff --git a/drivers/virtio/virtio_pci_modern_dev.c b/drivers/virtio/virtio_pci_modern_dev.c
> > > > index fa2a9445bb18..869cb46bef96 100644
> > > > --- a/drivers/virtio/virtio_pci_modern_dev.c
> > > > +++ b/drivers/virtio/virtio_pci_modern_dev.c
> > > > @@ -3,6 +3,7 @@
> > > >  #include <linux/virtio_pci_modern.h>
> > > >  #include <linux/module.h>
> > > >  #include <linux/pci.h>
> > > > +#include <linux/delay.h>
> > > >
> > > >  /*
> > > >   * vp_modern_map_capability - map a part of virtio pci capability
> > > > @@ -474,6 +475,44 @@ void vp_modern_set_status(struct virtio_pci_modern_device *mdev,
> > > >  }
> > > >  EXPORT_SYMBOL_GPL(vp_modern_set_status);
> > > >
> > > > +/*
> > > > + * vp_modern_get_queue_reset - get the queue reset status
> > > > + * @mdev: the modern virtio-pci device
> > > > + * @index: queue index
> > > > + */
> > > > +int vp_modern_get_queue_reset(struct virtio_pci_modern_device *mdev, u16 index)
> > > > +{
> > > > +	struct virtio_pci_modern_common_cfg __iomem *cfg;
> > > > +
> > > > +	cfg = (struct virtio_pci_modern_common_cfg __iomem *)mdev->common;
> > > > +
> > > > +	vp_iowrite16(index, &cfg->cfg.queue_select);
> > > > +	return vp_ioread16(&cfg->queue_reset);
> > > > +}
> > > > +EXPORT_SYMBOL_GPL(vp_modern_get_queue_reset);
> > > > +
> > >
> > > Actually, this does not validate that the config structure is big
> > > enough. So it can access some unrelated memory. Don't know whether
> > > that's exploitable e.g. for CoCo but not nice, anyway.
> > > Need to validate the size and disable reset if it's too small.
> >
> >
> > static int vp_modern_disable_vq_and_reset(struct virtqueue *vq)
> > {
> > 	struct virtio_pci_device *vp_dev = to_vp_device(vq->vdev);
> > 	struct virtio_pci_modern_device *mdev = &vp_dev->mdev;
> > 	struct virtio_pci_vq_info *info;
> > 	unsigned long flags;
> >
> > ->	if (!virtio_has_feature(vq->vdev, VIRTIO_F_RING_RESET))
> > 		return -ENOENT;
> >
> > 	vp_modern_set_queue_reset(mdev, vq->index);
> >
> >
> > I checked VIRTIO_F_RING_RESET before call this.
>
> Yes but the point is that virtio is used with untrusted devices
> (e.g. for SEV/TDX), so you can't really assume config structures
> are in sync with feature bits.

I see.

I will post a patch to check the length of the common cfg.

Thanks.


>
>
> > Do you mean, we should put the check to this function.
> >
> >
> > Thanks.
> >
> >
> >
> > >
> > >
> > > > +/*
> > > > + * vp_modern_set_queue_reset - reset the queue
> > > > + * @mdev: the modern virtio-pci device
> > > > + * @index: queue index
> > > > + */
> > > > +void vp_modern_set_queue_reset(struct virtio_pci_modern_device *mdev, u16 index)
> > > > +{
> > > > +	struct virtio_pci_modern_common_cfg __iomem *cfg;
> > > > +
> > > > +	cfg = (struct virtio_pci_modern_common_cfg __iomem *)mdev->common;
> > > > +
> > > > +	vp_iowrite16(index, &cfg->cfg.queue_select);
> > > > +	vp_iowrite16(1, &cfg->queue_reset);
> > > > +
> > > > +	while (vp_ioread16(&cfg->queue_reset))
> > > > +		msleep(1);
> > > > +
> > > > +	while (vp_ioread16(&cfg->cfg.queue_enable))
> > > > +		msleep(1);
> > > > +}
> > > > +EXPORT_SYMBOL_GPL(vp_modern_set_queue_reset);
> > > > +
> > > >  /*
> > > >   * vp_modern_queue_vector - set the MSIX vector for a specific virtqueue
> > > >   * @mdev: the modern virtio-pci device
> > > > diff --git a/include/linux/virtio_pci_modern.h b/include/linux/virtio_pci_modern.h
> > > > index 05123b9a606f..c4eeb79b0139 100644
> > > > --- a/include/linux/virtio_pci_modern.h
> > > > +++ b/include/linux/virtio_pci_modern.h
> > > > @@ -113,4 +113,6 @@ void __iomem * vp_modern_map_vq_notify(struct virtio_pci_modern_device *mdev,
> > > >  				       u16 index, resource_size_t *pa);
> > > >  int vp_modern_probe(struct virtio_pci_modern_device *mdev);
> > > >  void vp_modern_remove(struct virtio_pci_modern_device *mdev);
> > > > +int vp_modern_get_queue_reset(struct virtio_pci_modern_device *mdev, u16 index);
> > > > +void vp_modern_set_queue_reset(struct virtio_pci_modern_device *mdev, u16 index);
> > > >  #endif
> > > > --
> > > > 2.31.0
> > >
>