vdpa: Protect vdpa reset with cf_mutex

Call reset using the wrapper function vdpa_reset() to make sure the
operation is serialized with cf_mutex.

This comes to protect from the following possible scenario:

vhost_vdpa_set_status() could call the reset op. Since the call is not
protected by cf_mutex, a netlink thread calling vdpa_dev_config_fill
could get passed the VIRTIO_CONFIG_S_FEATURES_OK check in
vdpa_dev_config_fill() and end up reporting wrong features.

Fixes: 5f6e85953d8f ("vdpa: Read device configuration only if FEATURES_OK")
Signed-off-by: NEli Cohen <elic@nvidia.com>
Link: https://lore.kernel.org/r/20220111183400.38418-3-elic@nvidia.comSigned-off-by: NMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: Si-Wei Liu<si-wei.liu@oracle.com>
Acked-by: NJason Wang <jasowang@redhat.com>

drivers/vhost/vdpa.c

@@ -178,7 +178,7 @@ static long vhost_vdpa_set_status(struct vhost_vdpa *v, u8 __user *statusp)
 			vhost_vdpa_unsetup_vq_irq(v, i);
 
 	if (status == 0) {
-		ret = ops->reset(vdpa);
+		ret = vdpa_reset(vdpa);
 		if (ret)
 			return ret;
 	} else