linux-kernel - RE: [PATCH 1/1] Drivers: input: serio: New driver to support Hyper-V synthetic keyboard

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Message-ID: <baabf219b12b40de8e17b029e621e079@SN2PR03MB061.namprd03.prod.outlook.com>
Date:	Mon, 16 Sep 2013 16:56:03 +0000
From:	KY Srinivasan <kys@...rosoft.com>
To:	Dan Carpenter <dan.carpenter@...cle.com>
CC:	"olaf@...fle.de" <olaf@...fle.de>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"jasowang@...hat.com" <jasowang@...hat.com>,
	"dmitry.torokhov@...il.com" <dmitry.torokhov@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"vojtech@...e.cz" <vojtech@...e.cz>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	"apw@...onical.com" <apw@...onical.com>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>
Subject: RE: [PATCH 1/1] Drivers: input: serio: New driver to support
 Hyper-V synthetic keyboard



> -----Original Message-----
> From: Dan Carpenter [mailto:dan.carpenter@...cle.com]
> Sent: Monday, September 16, 2013 8:06 AM
> To: KY Srinivasan
> Cc: olaf@...fle.de; gregkh@...uxfoundation.org; jasowang@...hat.com;
> dmitry.torokhov@...il.com; linux-kernel@...r.kernel.org; vojtech@...e.cz;
> linux-input@...r.kernel.org; apw@...onical.com; devel@...uxdriverproject.org
> Subject: Re: [PATCH 1/1] Drivers: input: serio: New driver to support Hyper-V
> synthetic keyboard
> 
> On Mon, Sep 16, 2013 at 02:46:24PM +0000, KY Srinivasan wrote:
> > > > +			case VM_PKT_DATA_INBAND:
> > > > +				hv_kbd_on_receive(device, desc);
> > >
> > > This is the error handling I mentioned at the top.  hv_kbd_on_receive()
> > > doesn't take into consideration the amount of data we recieved, it
> > > trusts the offset we recieved from the user.  There is an out of bounds
> > > read.
> >
> > What user are you referring to. The message is sent by the host - the user
> keystroke
> > is normalized into a fixed size packet by the host and sent to the  guest. We will
> parse this
> > packet, based on the host specified layout here.
> >
> 
> The user means the hypervisor, yes.
> 
> I don't want the hypervisor accessing outside of the buffer.  It is
> robustness issue.  Just check the offset against "bytes_recvd".  It's
> not complicated.

At the outset, let me apologize for not understanding your concern.
You say: " I don't want the hypervisor accessing outside of the buffer"
Where did you see the hypervisor accessing anything outside the buffer?
The buffer is allocated by this driver and a packet from vmbus is read into this
buffer - this is the call to vmbus_recvpacket(). If the specified buffer is smaller
than the packet that needs to be read, then nothing will be read. Once the read
completes, we can be sure we have read a valid packet and can proceed to parse it in
this driver.

I don't want to be argumentative, I am just not seeing the issue.

Regards,

K. Y
 
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