From: KY Srinivasan <kys@microsoft.com>
To: Dan Carpenter <dan.carpenter@oracle.com>
CC: "olaf@aepfle.de" <olaf@aepfle.de>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "jasowang@redhat.com" <jasowang@redhat.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "apw@canonical.com" <apw@canonical.com>,
        "devel@linuxdriverproject.org" <devel@linuxdriverproject.org>
Subject: RE: [PATCH 1/1] Drivers: hv: Implement the file copy service
Thread-Topic: [PATCH 1/1] Drivers: hv: Implement the file copy service
Thread-Index: AQHPDMVZ9zrtMOoYp0KOm7oSIbZbR5p8AmiAgAC00tCAAByZgIAADLTg
Date: Thu, 9 Jan 2014 21:05:05 +0000
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> -----Original Message-----
> From: Dan Carpenter [mailto:dan.carpenter@oracle.com]
> Sent: Thursday, January 09, 2014 12:09 PM
> To: KY Srinivasan
> Cc: olaf@aepfle.de; gregkh@linuxfoundation.org; jasowang@redhat.com; linux-
> kernel@vger.kernel.org; apw@canonical.com; devel@linuxdriverproject.org
> Subject: Re: [PATCH 1/1] Drivers: hv: Implement the file copy service
> 
> We've had this discussion before where you urge me to trust the host...

I am just implementing the protocol specification given by the host. If I cannot trust the
specified protocol, I am not sure what else can be done here. 

> 
>  Problem: This code is racy.
> Solution: The host will only send one message at a time.

The code is not racy given the protocol that is specified. While I could have 
blindly trusted the host, this driver code actually reads only one packet at a time.
When we get a transaction from the host, we do not process any more transactions until
the current transaction is fully processed. So what is the race condition here?

> 
> Now I have to audit the user space code on the host and I don't feel
> like doing that so you win.

I don't think you need to audit any code.

> 
> I wish we had a better way to do IPC.  If kdbus were ready, that might
> have worked for this, and it's a better solution because both sender and
> reciever code will be written in a less trusting way.

I am not sure how kdbus would help you here. We are talking about communicating
between the host and the guest here. 

K. Y
> 
> regards,
> dan carpenter

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