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

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Message-ID: <20130916150548.GO25896@mwanda>
Date:	Mon, 16 Sep 2013 18:05:48 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	KY Srinivasan <kys@...rosoft.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

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.

If you have a different place where the guest does this then tell me
which function to look at.

regards,
dan carpenter
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