On Sat, 3 Oct 2020 09:58:59 +0800
Jason Wang <jasowang@xxxxxxxxxx> wrote:
>
> On 2020/9/30 上午12:30, Greg Kurz wrote:
> > When the IOTLB device is enabled, the log_guest_addr that is passed by
> > userspace to the VHOST_SET_VRING_ADDR ioctl, and which is then written
> > to vq->log_addr, is a GIOVA. All writes to this address are translated
> > by log_user() to writes to an HVA, and then ultimately logged through
> > the corresponding GPAs in log_write_hva(). No logging will ever occur
> > with vq->log_addr in this case. It is thus wrong to pass vq->log_addr
> > and log_guest_addr to log_access_vq() which assumes they are actual
> > GPAs.
> >
> > Introduce a new vq_log_used_access_ok() helper that only checks accesses
> > to the log for the used structure when there isn't an IOTLB device around.
> >
> > Signed-off-by: Greg Kurz <groug@xxxxxxxx>
> > ---
> > drivers/vhost/vhost.c | 23 +++++++++++++++++++----
> > 1 file changed, 19 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> > index c3b49975dc28..5996e32fa818 100644
> > --- a/drivers/vhost/vhost.c
> > +++ b/drivers/vhost/vhost.c
> > @@ -1370,6 +1370,20 @@ bool vhost_log_access_ok(struct vhost_dev *dev)
> > }
> > EXPORT_SYMBOL_GPL(vhost_log_access_ok);
> >
> > +static bool vq_log_used_access_ok(struct vhost_virtqueue *vq,
> > + void __user *log_base,
> > + bool log_used,
> > + u64 log_addr,
> > + size_t log_size)
> > +{
> > + /* If an IOTLB device is present, log_addr is a GIOVA that
> > + * will never be logged by log_used(). */
> > + if (vq->iotlb)
> > + return true;
> > +
> > + return !log_used || log_access_ok(log_base, log_addr, log_size);
> > +}
> > +
> > /* Verify access for write logging. */
> > /* Caller should have vq mutex and device mutex */
> > static bool vq_log_access_ok(struct vhost_virtqueue *vq,
> > @@ -1377,8 +1391,8 @@ static bool vq_log_access_ok(struct vhost_virtqueue *vq,
> > {
> > return vq_memory_access_ok(log_base, vq->umem,
> > vhost_has_feature(vq, VHOST_F_LOG_ALL)) &&
> > - (!vq->log_used || log_access_ok(log_base, vq->log_addr,
> > - vhost_get_used_size(vq, vq->num)));
> > + vq_log_used_access_ok(vq, log_base, vq->log_used, vq->log_addr,
> > + vhost_get_used_size(vq, vq->num));
> > }
> >
> > /* Can we start vq? */
> > @@ -1517,8 +1531,9 @@ static long vhost_vring_set_addr(struct vhost_dev *d,
> > return -EINVAL;
> >
> > /* Also validate log access for used ring if enabled. */
> > - if ((a.flags & (0x1 << VHOST_VRING_F_LOG)) &&
> > - !log_access_ok(vq->log_base, a.log_guest_addr,
> > + if (!vq_log_used_access_ok(vq, vq->log_base,
> > + a.flags & (0x1 << VHOST_VRING_F_LOG),
> > + a.log_guest_addr,
> > sizeof *vq->used +
> > vq->num * sizeof *vq->used->ring))
>
>
> It looks to me that we should use vhost_get_used_size() which takes
> event into account.
>
> Any reason that we can't reuse vq_log_access_ok() here?
>
No reason indeed but I'll fix this in a preliminary patch, and
send a v2 shortly.
Cheers,
--
Greg
> Thanks
>
>
> > return -EINVAL;
> >
> >
>
