vhost/scsi: truncate T10 PI iov_iter to prot_bytes

Commands with protection information included were not truncating the
protection iov_iter to the number of protection bytes in the command.
This resulted in vhost_scsi mis-calculating the size of the protection
SGL in vhost_scsi_calc_sgls(), and including both the protection and
data SG entries in the protection SGL.

Fixes: 09b13fa ("vhost/scsi: Add ANY_LAYOUT support in vhost_scsi_handle_vq")
Signed-off-by: Greg Edwards <gedwards@ddn.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Fixes: 09b13fa
Cc: stable@vger.kernel.org
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

drivers/vhost/scsi.c

@@ -964,7 +964,8 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
  prot_bytes = vhost32_to_cpu(vq, v_req_pi.pi_bytesin);
  }
  /*
- * Set prot_iter to data_iter, and advance past any
+ * Set prot_iter to data_iter and truncate it to
+ * prot_bytes, and advance data_iter past any
  * preceeding prot_bytes that may be present.
  *
  * Also fix up the exp_data_len to reflect only the
@@ -973,6 +974,7 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
  if (prot_bytes) {
  exp_data_len -= prot_bytes;
  prot_iter = data_iter;
+ iov_iter_truncate(&prot_iter, prot_bytes);
  iov_iter_advance(&data_iter, prot_bytes);
  }
  tag = vhost64_to_cpu(vq, v_req_pi.tag);