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From:   "Michael Kelley (LINUX)" <mikelley@microsoft.com>
To:     "Andrea Parri (Microsoft)" <parri.andrea@gmail.com>,
        KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Wei Liu <wei.liu@kernel.org>, Dexuan Cui <decui@microsoft.com>,
        Stefano Garzarella <sgarzare@redhat.com>,
        David Miller <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>
CC:     "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        "virtualization@lists.linux-foundation.org" 
        <virtualization@lists.linux-foundation.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [RFC PATCH 2/6] hv_sock: Copy packets sent by Hyper-V out of the
 ring buffer
Thread-Topic: [RFC PATCH 2/6] hv_sock: Copy packets sent by Hyper-V out of the
 ring buffer
Thread-Index: AQHYT3fHt6IPwxyLaEamUw9BuXqN2azvm6mA
Date:   Fri, 15 Apr 2022 03:33:31 +0000
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References: <20220413204742.5539-1-parri.andrea@gmail.com>
 <20220413204742.5539-3-parri.andrea@gmail.com>
In-Reply-To: <20220413204742.5539-3-parri.andrea@gmail.com>
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From: Andrea Parri (Microsoft) <parri.andrea@gmail.com> Sent: Wednesday, Ap=
ril 13, 2022 1:48 PM
>=20
> Pointers to VMbus packets sent by Hyper-V are used by the hv_sock driver
> within the gues VM.  Hyper-V can send packets with erroneous values or

s/gues/guest/

> modify packet fields after they are processed by the guest.  To defend
> against these scenarios, copy the incoming packet after validating its
> length and offset fields using hv_pkt_iter_{first,next}().  In this way,
> the packet can no longer be modified by the host.
>=20
> Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
> ---
>  net/vmw_vsock/hyperv_transport.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>=20
> diff --git a/net/vmw_vsock/hyperv_transport.c b/net/vmw_vsock/hyperv_tran=
sport.c
> index 943352530936e..8c37d07017fc4 100644
> --- a/net/vmw_vsock/hyperv_transport.c
> +++ b/net/vmw_vsock/hyperv_transport.c
> @@ -78,6 +78,9 @@ struct hvs_send_buf {
>  					 ALIGN((payload_len), 8) + \
>  					 VMBUS_PKT_TRAILER_SIZE)
>=20
> +/* Upper bound on the size of a VMbus packet for hv_sock */
> +#define HVS_MAX_PKT_SIZE	HVS_PKT_LEN(HVS_MTU_SIZE)
> +
>  union hvs_service_id {
>  	guid_t	srv_id;
>=20
> @@ -378,6 +381,8 @@ static void hvs_open_connection(struct vmbus_channel =
*chan)
>  		rcvbuf =3D ALIGN(rcvbuf, HV_HYP_PAGE_SIZE);
>  	}
>=20
> +	chan->max_pkt_size =3D HVS_MAX_PKT_SIZE;
> +
>  	ret =3D vmbus_open(chan, sndbuf, rcvbuf, NULL, 0, hvs_channel_cb,
>  			 conn_from_host ? new : sk);
>  	if (ret !=3D 0) {
> @@ -602,7 +607,7 @@ static ssize_t hvs_stream_dequeue(struct vsock_sock *=
vsk,
> struct msghdr *msg,
>  		return -EOPNOTSUPP;
>=20
>  	if (need_refill) {
> -		hvs->recv_desc =3D hv_pkt_iter_first_raw(hvs->chan);
> +		hvs->recv_desc =3D hv_pkt_iter_first(hvs->chan);
>  		if (!hvs->recv_desc)
>  			return -ENOBUFS;
>  		ret =3D hvs_update_recv_data(hvs);
> @@ -618,7 +623,7 @@ static ssize_t hvs_stream_dequeue(struct vsock_sock *=
vsk,
> struct msghdr *msg,
>=20
>  	hvs->recv_data_len -=3D to_read;
>  	if (hvs->recv_data_len =3D=3D 0) {
> -		hvs->recv_desc =3D hv_pkt_iter_next_raw(hvs->chan, hvs->recv_desc);
> +		hvs->recv_desc =3D hv_pkt_iter_next(hvs->chan, hvs->recv_desc);
>  		if (hvs->recv_desc) {
>  			ret =3D hvs_update_recv_data(hvs);
>  			if (ret)
> --
> 2.25.1