linux-kernel - RE: [PATCH 2/4] Drivers: hv: Support the newly introduced KVP messages in the driver

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Date:	Thu, 15 Mar 2012 23:36:16 +0000
From:	KY Srinivasan <kys@...rosoft.com>
To:	Dan Carpenter <dan.carpenter@...cle.com>
CC:	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"ohering@...e.com" <ohering@...e.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"virtualization@...ts.osdl.org" <virtualization@...ts.osdl.org>,
	Alan Stern <stern@...land.harvard.edu>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>
Subject: RE: [PATCH 2/4] Drivers: hv: Support the newly introduced KVP
 messages in the driver



> -----Original Message-----
> From: Dan Carpenter [mailto:dan.carpenter@...cle.com]
> Sent: Monday, March 12, 2012 9:04 AM
> To: KY Srinivasan
> Cc: gregkh@...uxfoundation.org; ohering@...e.com; linux-
> kernel@...r.kernel.org; virtualization@...ts.osdl.org; Alan Stern;
> devel@...uxdriverproject.org
> Subject: Re: [PATCH 2/4] Drivers: hv: Support the newly introduced KVP
> messages in the driver
> 
> On Mon, Mar 12, 2012 at 12:36:53PM +0000, KY Srinivasan wrote:
> > Dan,
> > I am sorry for not being as precise as I should be:
> > utf16s_to_utf8s() takes two length parameters - the length of the utf16 string
> > that is to be converted and the second the length of the utf8 output string.
> > The windows host manipulates all string in utf16 encoding and the string we get
> > from the host is guaranteed to be less than or equal to MAX value that we have
> > including the terminating character. In my code, I simply pass the length of the
> > utf16 string as received from the host.
> >
> > The parameter that I am currently passing MAX length value is the "maxout"
> > parameter of the utf16s_utf8s() function. This by definition is the size of the
> > output buffer and in this case it happens to be MAX characters big.
> >
> 
> I also think I'm not being as clear as I should...  I understand
> that you trust the input; I'm say that for correctness sake you
> should specify a output size which leaves room for the NUL char.
> 
> I can't say I know this code very well so I could be wrong, but it's
> what we do inside usb_string() for example.  Can someone who knows
> the code check if we should do something like this:
> 

Dan, 

Sorry I could not get back to you earlier. You are right, in that I am trusting
the host! I am of the firm belief that in a virtualized environment, if you don't trust
the host, there is not a whole lot you can do in a guest! I have had this arguments 
with other on this mailing list in the past. Having said that, I think we have spent more
time debating this than we should; your proposal is reasonable and I will go ahead and
re-spin those patches based on your comments. I should be posting them shortly.

Regards,

K. Y

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