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

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Date:   Thu, 25 Jun 2020 18:57:51 +0000
From:   Haiyang Zhang <haiyangz@...rosoft.com>
To:     Andres Beltran <lkmlabelt@...il.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>
CC:     "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Michael Kelley <mikelley@...rosoft.com>,
        "parri.andrea@...il.com" <parri.andrea@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH 3/3] hv_netvsc: Use vmbus_requestor to generate
 transaction IDs for VMBus hardening



> -----Original Message-----
> From: Andres Beltran <lkmlabelt@...il.com>
> Sent: Thursday, June 25, 2020 11:37 AM
> To: KY Srinivasan <kys@...rosoft.com>; Haiyang Zhang
> <haiyangz@...rosoft.com>; Stephen Hemminger <sthemmin@...rosoft.com>;
> wei.liu@...nel.org
> Cc: linux-hyperv@...r.kernel.org; linux-kernel@...r.kernel.org; Michael
> Kelley <mikelley@...rosoft.com>; parri.andrea@...il.com; Andres Beltran
> <lkmlabelt@...il.com>; David S. Miller <davem@...emloft.net>; Jakub
> Kicinski <kuba@...nel.org>; netdev@...r.kernel.org
> 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@...emloft.net>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Cc: netdev@...r.kernel.org
> Signed-off-by: Andres Beltran <lkmlabelt@...il.com>
> ---
>  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