RE: [PATCH 1/1] Drivers: input: serio: New driver to supportHyper-V synthetic keyboard

[KY Srinivasan]

> -----Original Message-----
> From: Dan Carpenter [mailto:dan.carpenter@xxxxxxxxxx]
> Sent: Monday, September 16, 2013 8:06 AM
> To: KY Srinivasan
> Cc: olaf@xxxxxxxxx; gregkh@xxxxxxxxxxxxxxxxxxx; jasowang@xxxxxxxxxx;
> dmitry.torokhov@xxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; vojtech@xxxxxxx;
> linux-input@xxxxxxxxxxxxxxx; apw@xxxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx
> 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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