RE: [PATCH net-next, 2/2] hv_netvsc: Add range checking for rx packet offset and length

[Haiyang Zhang]

> -----Original Message-----
> From: Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx>
> Sent: Tuesday, March 27, 2018 11:23 AM
> To: Haiyang Zhang <haiyangz@xxxxxxxxxxxxxxxxx>
> Cc: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>; davem@xxxxxxxxxxxxx;
> netdev@xxxxxxxxxxxxxxx; olaf@xxxxxxxxx; Stephen Hemminger
> <sthemmin@xxxxxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx;
> devel@xxxxxxxxxxxxxxxxxxxxxx; vkuznets@xxxxxxxxxx
> Subject: Re: [PATCH net-next, 2/2] hv_netvsc: Add range checking for rx packet
> offset and length
> 
> On Thu, 22 Mar 2018 12:01:14 -0700
> Haiyang Zhang <haiyangz@xxxxxxxxxxxxxxxxx> wrote:
> 
> > From: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
> >
> > This patch adds range checking for rx packet offset and length.
> > It may only happen if there is a host side bug.
> >
> > Signed-off-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
> > ---
> >  drivers/net/hyperv/hyperv_net.h |  1 +
> >  drivers/net/hyperv/netvsc.c     | 17 +++++++++++++++--
> >  2 files changed, 16 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/hyperv/hyperv_net.h
> > b/drivers/net/hyperv/hyperv_net.h index 0db3bd1ea06f..49c05ac894e5
> > 100644
> > --- a/drivers/net/hyperv/hyperv_net.h
> > +++ b/drivers/net/hyperv/hyperv_net.h
> > @@ -793,6 +793,7 @@ struct netvsc_device {
> >
> >  	/* Receive buffer allocated by us but manages by NetVSP */
> >  	void *recv_buf;
> > +	u32 recv_buf_size; /* allocated bytes */
> >  	u32 recv_buf_gpadl_handle;
> >  	u32 recv_section_cnt;
> >  	u32 recv_section_size;
> > diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
> > index 1ddb2c39b6e4..a6700d65f206 100644
> > --- a/drivers/net/hyperv/netvsc.c
> > +++ b/drivers/net/hyperv/netvsc.c
> > @@ -289,6 +289,8 @@ static int netvsc_init_buf(struct hv_device *device,
> >  		goto cleanup;
> >  	}
> >
> > +	net_device->recv_buf_size = buf_size;
> > +
> >  	/*
> >  	 * Establish the gpadl handle for this buffer on this
> >  	 * channel.  Note: This call uses the vmbus connection rather @@
> > -1095,11 +1097,22 @@ static int netvsc_receive(struct net_device
> > *ndev,
> >
> >  	/* Each range represents 1 RNDIS pkt that contains 1 ethernet frame */
> >  	for (i = 0; i < count; i++) {
> > -		void *data = recv_buf
> > -			+ vmxferpage_packet->ranges[i].byte_offset;
> > +		u32 offset = vmxferpage_packet->ranges[i].byte_offset;
> >  		u32 buflen = vmxferpage_packet->ranges[i].byte_count;
> > +		void *data;
> >  		int ret;
> >
> > +		if (unlikely(offset + buflen > net_device->recv_buf_size)) {
> > +			status = NVSP_STAT_FAIL;
> > +			netif_err(net_device_ctx, rx_err, ndev,
> > +				  "Packet offset:%u + len:%u too big\n",
> > +				  offset, buflen);
> > +
> > +			continue;
> > +		}
> > +
> 
> If one part of the RNDIS packet is wrong then the whole receive buffer is
> damaged. Just return, don't continue.
> 
> It could really just be a statistic and a one shot log message.

I will let the loop terminates and send NVSP status fail to the host.

For statistics, this range check is to catch potential host side issues, just like
these checks in the same function earlier:
	/* Make sure this is a valid nvsp packet */
	if (unlikely(nvsp->hdr.msg_type != NVSP_MSG1_TYPE_SEND_RNDIS_PKT)) {
		netif_err(net_device_ctx, rx_err, ndev,
			  "Unknown nvsp packet type received %u\n",
			  nvsp->hdr.msg_type);
		return 0;
	}

	if (unlikely(vmxferpage_packet->xfer_pageset_id != NETVSC_RECEIVE_BUFFER_ID)) {
		netif_err(net_device_ctx, rx_err, ndev,
			  "Invalid xfer page set id - expecting %x got %x\n",
			  NETVSC_RECEIVE_BUFFER_ID,
			  vmxferpage_packet->xfer_pageset_id);
		return 0;
	}

If these kinds of errors need statistics, there will be many stat variables... Maybe we 
should just create one stat variable for all of the "invalid format from host"?

Thanks,
- Haiyang