Re: [PATCH] vhost: Check for valid vdev in vhost_backend_handle_iotlb_msg

[Eugenio Perez Martin]

Version 2 of ("vhost-user: Check for iotlb callback in iotlb_miss") [1].

Starting a new series, since the title does not reflect the changes anymore.

Thanks!

[1] 20210127204449.745365-1-eperezma@redhat.com/">https://patchew.org/QEMU/20210127204449.745365-1-eperezma@redhat.com/

On Fri, Jan 29, 2021 at 10:08 AM Eugenio Pérez <eperezma@redhat.com> wrote:
>
> Not checking this can lead to invalid dev->vdev member access in
> vhost_device_iotlb_miss if backend issue an iotlb message in a bad
> timing, either maliciously or by a bug.
>
> Reproduced rebooting a guest with testpmd in txonly forward mode.
>  #0  0x0000559ffff94394 in vhost_device_iotlb_miss (
>      dev=dev@entry=0x55a0012f6680, iova=10245279744, write=1)
>      at ../hw/virtio/vhost.c:1013
>  #1  0x0000559ffff9ac31 in vhost_backend_handle_iotlb_msg (
>      imsg=0x7ffddcfd32c0, dev=0x55a0012f6680)
>      at ../hw/virtio/vhost-backend.c:411
>  #2  vhost_backend_handle_iotlb_msg (dev=dev@entry=0x55a0012f6680,
>      imsg=imsg@entry=0x7ffddcfd32c0)
>      at ../hw/virtio/vhost-backend.c:404
>  #3  0x0000559fffeded7b in slave_read (opaque=0x55a0012f6680)
>      at ../hw/virtio/vhost-user.c:1464
>  #4  0x000055a0000c541b in aio_dispatch_handler (
>      ctx=ctx@entry=0x55a0010a2120, node=0x55a0012d9e00)
>      at ../util/aio-posix.c:329
>
> Fixes: 6dcdd06e3b ("spec/vhost-user spec: Add IOMMU support")
> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> ---
>  hw/virtio/vhost-backend.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c
> index 222bbcc62d..31b33bde37 100644
> --- a/hw/virtio/vhost-backend.c
> +++ b/hw/virtio/vhost-backend.c
> @@ -406,6 +406,11 @@ int vhost_backend_handle_iotlb_msg(struct vhost_dev *dev,
>  {
>      int ret = 0;
>
> +    if (unlikely(!dev->vdev)) {
> +        error_report("Unexpected IOTLB message when virtio device is 
> stopped");
> +        return -EINVAL;
> +    }
> +
>      switch (imsg->type) {
>      case VHOST_IOTLB_MISS:
>          ret = vhost_device_iotlb_miss(dev, imsg->iova,
> --
> 2.27.0
>
>