RE: [PATCH 3/3] hv_netvsc: Use vmbus_requestor to generate transaction IDs for VMBus hardening

[Haiyang Zhang]

> -----Original Message-----
> From: Andres Beltran <lkmlabelt@xxxxxxxxx>
> Sent: Thursday, June 25, 2020 11:37 AM
> To: KY Srinivasan <kys@xxxxxxxxxxxxx>; Haiyang Zhang
> <haiyangz@xxxxxxxxxxxxx>; Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>;
> wei.liu@xxxxxxxxxx
> Cc: linux-hyperv@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Michael
> Kelley <mikelley@xxxxxxxxxxxxx>; parri.andrea@xxxxxxxxx; Andres Beltran
> <lkmlabelt@xxxxxxxxx>; David S. Miller <davem@xxxxxxxxxxxxx>; Jakub
> Kicinski <kuba@xxxxxxxxxx>; netdev@xxxxxxxxxxxxxxx
> Subject: [PATCH 3/3] hv_netvsc: Use vmbus_requestor to generate transaction
> IDs for VMBus hardening
> 
> Currently, pointers to guest memory are passed to Hyper-V as
> transaction IDs in netvsc. In the face of errors or malicious
> behavior in Hyper-V, netvsc should not expose or trust the transaction
> IDs returned by Hyper-V to be valid guest memory addresses. Instead,
> use small integers generated by vmbus_requestor as requests
> (transaction) IDs.
> 
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
> Cc: netdev@xxxxxxxxxxxxxxx
> Signed-off-by: Andres Beltran <lkmlabelt@xxxxxxxxx>
> ---
>  drivers/net/hyperv/hyperv_net.h   | 10 +++++
>  drivers/net/hyperv/netvsc.c       | 75 +++++++++++++++++++++++++------
>  drivers/net/hyperv/rndis_filter.c |  1 +
>  include/linux/hyperv.h            |  1 +
>  4 files changed, 73 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
> index abda736e7c7d..14735c98e798 100644
> --- a/drivers/net/hyperv/hyperv_net.h
> +++ b/drivers/net/hyperv/hyperv_net.h
> @@ -847,6 +847,16 @@ struct nvsp_message {
> 
>  #define NETVSC_XDP_HDRM 256
> 
> +#define NETVSC_MIN_OUT_MSG_SIZE (sizeof(struct vmpacket_descriptor) + \
> +				 sizeof(struct nvsp_message))
> +#define NETVSC_MIN_IN_MSG_SIZE sizeof(struct vmpacket_descriptor)
> +
> +/* Estimated requestor size:
> + * out_ring_size/min_out_msg_size + in_ring_size/min_in_msg_size
> + */
> +#define NETVSC_RQSTOR_SIZE (netvsc_ring_bytes /
> NETVSC_MIN_OUT_MSG_SIZE + \
> +			    netvsc_ring_bytes / NETVSC_MIN_IN_MSG_SIZE)

Please make the variable as the macro parameter for readability:
#define NETVSC_RQSTOR_SIZE(ringbytes) (ringbytes / NETVSC_MIN_OUT_MSG_SIZE ...

Then put the actual variable name when you use the macro.

Thanks,
- Haiyang