netdev - Re: [PATCH] hv_netvsc: Add validation for untrusted Hyper-V values

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Date:   Fri, 14 Aug 2020 12:39:19 +0200
From:   Andrea Parri <parri.andrea@...il.com>
To:     Haiyang Zhang <haiyangz@...rosoft.com>
Cc:     Andres Beltran <lkmlabelt@...il.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        "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>,
        Saruhan Karademir <skarade@...rosoft.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH] hv_netvsc: Add validation for untrusted Hyper-V values

Hi Haiyang,

[I'm resuming this work by Andres.  Sorry for the delay.]


> >  	switch (nvsp_packet->hdr.msg_type) {
> >  	case NVSP_MSG_TYPE_INIT_COMPLETE:
> >  	case NVSP_MSG1_TYPE_SEND_RECV_BUF_COMPLETE:
> >  	case NVSP_MSG1_TYPE_SEND_SEND_BUF_COMPLETE:
> >  	case NVSP_MSG5_TYPE_SUBCHANNEL:
> > +		if (msglen < sizeof(struct nvsp_message)) {
> > +			netdev_err(ndev, "nvsp_msg5 length too small: %u\n",
> > +				   msglen);
> > +			return;
> > +		}
> 
> struct nvsp_message includes all message types, so its length is the longest type,
> The messages from older host version are not necessarily reaching the 
> sizeof(struct nvsp_message).

I split the check above into several checks, one for each "case", using
(what I understand are) the corresponding structures/sizeofs...

> 
> Testing on both new and older hosts are recommended, in case I didn't find out all issues
> like this one.

Sure, will do.

Thanks,
  Andrea