Virtualization - Apr 2022 - [PATCH 3/5] hv_sock: Add validation for untrusted Hyper-V values

From: Andrea Parri (Microsoft) <parri.andrea at gmail.com> Sent:
Wednesday, April 20, 2022 1:07 PM
> 
> For additional robustness in the face of Hyper-V errors or malicious
> behavior, validate all values that originate from packets that Hyper-V
> has sent to the guest in the host-to-guest ring buffer.  Ensure that
> invalid values cannot cause data being copied out of the bounds of the
> source buffer in hvs_stream_dequeue().
> 
> Signed-off-by: Andrea Parri (Microsoft) <parri.andrea at gmail.com>
> ---
>  include/linux/hyperv.h           |  5 +++++
>  net/vmw_vsock/hyperv_transport.c | 11 +++++++++--
>  2 files changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
> index fe2e0179ed51e..55478a6810b60 100644
> --- a/include/linux/hyperv.h
> +++ b/include/linux/hyperv.h
> @@ -1663,6 +1663,11 @@ static inline u32 hv_pkt_datalen(const struct
> vmpacket_descriptor *desc)
>  	return (desc->len8 << 3) - (desc->offset8 << 3);
>  }
> 
> +/* Get packet length associated with descriptor */
> +static inline u32 hv_pkt_len(const struct vmpacket_descriptor *desc)
> +{
> +	return desc->len8 << 3;
> +}
> 
>  struct vmpacket_descriptor *
>  hv_pkt_iter_first_raw(struct vmbus_channel *channel);
> diff --git a/net/vmw_vsock/hyperv_transport.c
b/net/vmw_vsock/hyperv_transport.c
> index 8c37d07017fc4..092cadc2c866d 100644
> --- a/net/vmw_vsock/hyperv_transport.c
> +++ b/net/vmw_vsock/hyperv_transport.c
> @@ -577,12 +577,19 @@ static bool hvs_dgram_allow(u32 cid, u32 port)
>  static int hvs_update_recv_data(struct hvsock *hvs)
>  {
>  	struct hvs_recv_buf *recv_buf;
> -	u32 payload_len;
> +	u32 pkt_len, payload_len;
> +
> +	pkt_len = hv_pkt_len(hvs->recv_desc);
> +
> +	/* Ensure the packet is big enough to read its header */
> +	if (pkt_len < HVS_HEADER_LEN)
> +		return -EIO;
> 
>  	recv_buf = (struct hvs_recv_buf *)(hvs->recv_desc + 1);
>  	payload_len = recv_buf->hdr.data_size;
> 
> -	if (payload_len > HVS_MTU_SIZE)
> +	/* Ensure the packet is big enough to read its payload */
> +	if (payload_len > pkt_len - HVS_HEADER_LEN || payload_len >
HVS_MTU_SIZE)
>  		return -EIO;
> 
>  	if (payload_len == 0)
> --
> 2.25.1
Reviewed-by: Michael Kelley <mikelley at microsoft.com>