Re: [PATCH v3] hw/net/virtio-net.c: fix crash in iov_copy()

[Michael S. Tsirkin]

On Thu, Jun 13, 2024 at 05:35:30PM +0300, Dmitry Frolov wrote:
> A crash found while fuzzing device virtio-net-socket-check-used.
> Assertion "offset == 0" in iov_copy() fails if less than guest_hdr_len bytes
> were transmited.
> 
> Signed-off-by: Dmitry Frolov <frolov@swemel.ru>

Reviewed-by: Michael S. Tsirkin <mst@redhat.com>

Jason, are you merging this?

> ---
> v1: https://patchew.org/QEMU/20240527133140.218300-2-frolov@swemel.ru/
> v2: broken
> v3: goto instead of repeating code
> ---
>  hw/net/virtio-net.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index 9c7e85caea..8f30972708 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -2735,6 +2735,10 @@ static int32_t virtio_net_flush_tx(VirtIONetQueue *q)
>           */
>          assert(n->host_hdr_len <= n->guest_hdr_len);
>          if (n->host_hdr_len != n->guest_hdr_len) {
> +            if (iov_size(out_sg, out_num) < n->guest_hdr_len) {
> +                virtio_error(vdev, "virtio-net header is invalid");
> +                goto detach;
> +            }
>              unsigned sg_num = iov_copy(sg, ARRAY_SIZE(sg),
>                                         out_sg, out_num,
>                                         0, n->host_hdr_len);
> -- 
> 2.43.0