linux-kernel - Re: [PATCH 03/17] Drivers: hv: kvp: Cleanup error handling in KVP

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Message-ID: <20120725144724.GD1894@decadent.org.uk>
Date:	Wed, 25 Jul 2012 15:47:25 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	KY Srinivasan <kys@...rosoft.com>
Cc:	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"virtualization@...ts.osdl.org" <virtualization@...ts.osdl.org>,
	"olaf@...fle.de" <olaf@...fle.de>,
	"apw@...onical.com" <apw@...onical.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH 03/17] Drivers: hv: kvp: Cleanup error handling in KVP

On Wed, Jul 25, 2012 at 02:10:05PM +0000, KY Srinivasan wrote:
> 
> 
> > -----Original Message-----
> > From: Ben Hutchings [mailto:ben@...adent.org.uk]
> > Sent: Tuesday, July 24, 2012 9:11 PM
> > To: KY Srinivasan
> > Cc: gregkh@...uxfoundation.org; linux-kernel@...r.kernel.org;
> > devel@...uxdriverproject.org; virtualization@...ts.osdl.org; olaf@...fle.de;
> > apw@...onical.com; netdev@...r.kernel.org
> > Subject: Re: [PATCH 03/17] Drivers: hv: kvp: Cleanup error handling in KVP
> > 
> > On Tue, 2012-07-24 at 09:01 -0700, K. Y. Srinivasan wrote:
> > > In preparation to implementing IP injection, cleanup the way we propagate
> > > and handle errors both in the driver as well as in the user level daemon.
> > >
> > > Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
> > > Reviewed-by: Haiyang Zhang <haiyangz@...rosoft.com>
> > > ---
> > >  drivers/hv/hv_kvp.c      |  112 +++++++++++++++++++++++++++++++++++++-
> > --------
> > >  include/linux/hyperv.h   |   17 +++++---
> > >  tools/hv/hv_kvp_daemon.c |   70 +++++++++++++++-------------
> > >  3 files changed, 138 insertions(+), 61 deletions(-)
> > >
> > > diff --git a/drivers/hv/hv_kvp.c b/drivers/hv/hv_kvp.c
> > > index 0012eed..9b7fc4a 100644
> > > --- a/drivers/hv/hv_kvp.c
> > > +++ b/drivers/hv/hv_kvp.c
> > [...]
> > > @@ -109,27 +154,52 @@ kvp_cn_callback(struct cn_msg *msg, struct
> > netlink_skb_parms *nsp)
> > >  {
> > >  	struct hv_kvp_msg *message;
> > >  	struct hv_kvp_msg_enumerate *data;
> > > +	int	error = 0;
> > >
> > >  	message = (struct hv_kvp_msg *)msg->data;
> > > -	switch (message->kvp_hdr.operation) {
> > > +
> > > +	/*
> > > +	 * If we are negotiating the version information
> > > +	 * with the daemon; handle that first.
> > > +	 */
> > > +
> > > +	if (in_hand_shake) {
> > > +		if (kvp_handle_handshake(message))
> > > +			in_hand_shake = false;
> > > +		return;
> > > +	}
> > > +
> > > +	/*
> > > +	 * Based on the version of the daemon, we propagate errors from the
> > > +	 * daemon differently.
> > > +	 */
> > > +
> > > +	data = &message->body.kvp_enum_data;
> > > +
> > > +	switch (dm_reg_value) {
> > >  	case KVP_OP_REGISTER:
> > > -		pr_info("KVP: user-mode registering done.\n");
> > > -		kvp_register();
> > > -		kvp_transaction.active = false;
> > > -		hv_kvp_onchannelcallback(kvp_transaction.kvp_context);
> > > +		/*
> > > +		 * Null string is used to pass back error condition.
> > > +		 */
> > > +		if (!strlen(data->data.key))
> > 
> > Do we know that the key is null-terminated here?  Shouldn't we just
> > check whether data->data.key[0] == 0?
> 
> Yes, currently we do return null string to indicate error.
[...]

So the kernel should assume userland input is always valid?

Ben.

-- 
Ben Hutchings
We get into the habit of living before acquiring the habit of thinking.
                                                              - Albert Camus
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