Re: [PATCH 2/3] SUNRPC: check rpcbind clients usage counter beforedecrement

[Stanislav Kinsbursky]

01.05.2012 01:45, J. Bruce Fields ÐÐÐÐÑÐÐ:
> On Fri, Apr 27, 2012 at 06:08:13PM +0400, Stanislav Kinsbursky wrote:
> > On 27.04.2012 17:55, J. Bruce Fields wrote:
> > > On Wed, Apr 25, 2012 at 05:37:49PM +0400, Stanislav Kinsbursky wrote:
> > > > Registering service with svc_bind() can fail. In this case service will be
> > > > destroyed and during destruction it will try to unregister itself from rpcbind.
> > > > In this case unregister have to be skipped.
> > > Isn't this a preexisting bug, in which case perhaps Trond should at it
> > > to his list of bugs to submit now?
> > Not it's not.
> >
> > Previously, in case of bind operations failure, rpcb_put_local()
> > wasn't called, but service data was destroyed instead:
> >
> > -	if (svc_uses_rpcbind(serv)) {
> > -		if (svc_rpcb_setup(serv, current->nsproxy->net_ns)<  0) {
> > -			kfree(serv->sv_pools);
> > -			kfree(serv);
> > -			return NULL;
> > -		}
> > -		if (!serv->sv_shutdown)
> > -			serv->sv_shutdown = svc_rpcb_cleanup;
> > -	}
> >
> > Now (with svc_bind() introduction) service can be created, but
> > svc_bind() could fail. And thus svc_destroy() have to be called.
> > Which will call rpcb_put_local().
> >
> > And the problem here that svc_bind() can fail before incrementing of
> > rpcb usage counter.
> OK, but then you're fixing a bug that you just introduced with the
> previous patch.
>
> So this should be combined with the previous patch.
>
> --b.

You, probably, right. I'll do this.
Thanks.

> > > > Signed-off-by: Stanislav Kinsbursky<skinsbursky@xxxxxxxxxxxxx>
> > > >
> > > > ---
> > > >   net/sunrpc/rpcb_clnt.c |   12 +++++++-----
> > > >   1 files changed, 7 insertions(+), 5 deletions(-)
> > > >
> > > > diff --git a/net/sunrpc/rpcb_clnt.c b/net/sunrpc/rpcb_clnt.c
> > > > index 78ac39f..4c38b33 100644
> > > > --- a/net/sunrpc/rpcb_clnt.c
> > > > +++ b/net/sunrpc/rpcb_clnt.c
> > > > @@ -180,14 +180,16 @@ void rpcb_put_local(struct net *net)
> > > >   	struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
> > > >   	struct rpc_clnt *clnt = sn->rpcb_local_clnt;
> > > >   	struct rpc_clnt *clnt4 = sn->rpcb_local_clnt4;
> > > > -	int shutdown;
> > > > +	int shutdown = 0;
> > > >
> > > >   	spin_lock(&sn->rpcb_clnt_lock);
> > > > -	if (--sn->rpcb_users == 0) {
> > > > -		sn->rpcb_local_clnt = NULL;
> > > > -		sn->rpcb_local_clnt4 = NULL;
> > > > +	if (sn->rpcb_users) {
> > > > +		if (--sn->rpcb_users == 0) {
> > > > +			sn->rpcb_local_clnt = NULL;
> > > > +			sn->rpcb_local_clnt4 = NULL;
> > > > +		}
> > > > +		shutdown = !sn->rpcb_users;
> > > >   	}
> > > > -	shutdown = !sn->rpcb_users;
> > > >   	spin_unlock(&sn->rpcb_clnt_lock);
> > > >
> > > >   	if (shutdown) {
> >
> > --
> > Best regards,
> > Stanislav Kinsbursky

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