Re: [PATCH 1/1] Drivers: input: serio: New driver to support Hyper-Vsynthetic keyboard

[Dan Carpenter]

On Mon, Sep 16, 2013 at 09:55:44PM +0000, KY Srinivasan wrote:
> 
> 
> > -----Original Message-----
> > From: Dan Carpenter [mailto:dan.carpenter@xxxxxxxxxx]
> > Sent: Monday, September 16, 2013 1:13 PM
> > To: KY Srinivasan
> > Cc: olaf@xxxxxxxxx; gregkh@xxxxxxxxxxxxxxxxxxx; jasowang@xxxxxxxxxx; Dmitry
> > Torokhov; 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 06:42:25PM +0000, KY Srinivasan wrote:
> > > Dan,
> > >
> > > Rolling the changes you have indicated is not the issue; this can trivially be
> > done.
> > > My contention is that it is not needed given that the underlying function is
> > already
> > > doing that. Look at the function  vmbus_recvpacket_raw() in
> > drivers/hv/channel.c.
> > >
> > 
> > I'm confused.
> > 
> > There is no mention of ->offset8 in vmbus_recvpacket_raw().
> 
> As you can see the vmbus_recvpacket_raw() ensures that the complete
> packet is read and if the buffer specified is not large enough nothing is 
> read. The packet header has information about the length of the packet
> and the offset where the payload is.  
> > 

No one is talking about the ->len8.  I'm saying that we should check
->offset8.

> > It's a good idea to add a check there but the lower levels don't know
> > about the sizeof(synth_kbd_protocol_response) so we would still need
> > something like my check.
> 
> Why would the lower level code need to know  anything about the layout of a
> particular message type. The lower level code is guaranteeing that a complete
> packet has been read in and that should be sufficient - assuming we trust the host.
> 

Of course, we don't need to check anything if we trust the host.  I said
that already.  Just add the check for robustness.

> We have already spent more time on this than we should; I will make the necessary
> changes.

Thank you.

regards,
dan carpenter

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