RE: [PATCH 03/17] Drivers: hv: kvp: Cleanup error handling in KVP

KY Srinivasan
2012-07-25T14:52:04Z

> -----Original Message-----
> From: Ben Hutchings [mailto:ben@decadent.org.uk]
> Sent: Wednesday, July 25, 2012 10:47 AM
> To: KY Srinivasan
> Cc: gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org;
> devel@linuxdriverproject.org; virtualization@lists.osdl.org; olaf@aepfle.de;
> apw@canonical.com; netdev@vger.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@decadent.org.uk]
> > > Sent: Tuesday, July 24, 2012 9:11 PM
> > > To: KY Srinivasan
> > > Cc: gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org;
> > > devel@linuxdriverproject.org; virtualization@lists.osdl.org; olaf@aepfle.de;
> > > apw@canonical.com; netdev@vger.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@microsoft.com>
> > > > Reviewed-by: Haiyang Zhang <haiyangz@microsoft.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?

Good point! This is the existing code and this patch-set cleans up all
the error handling and would not have this problem.

K. Y