Re: [PATCH v2 05/12] nfsd41: Backchannel: callback infrastructure

[Trond Myklebust <trond.myklebust@fys.uio.no>]

On Mon, 2009-09-14 at 16:39 -0400, J. Bruce Fields wrote:
> On Mon, Sep 14, 2009 at 04:17:32PM -0400, Trond Myklebust wrote:
> > On Mon, 2009-09-14 at 16:04 -0400, J. Bruce Fields wrote:
> > > On Mon, Sep 14, 2009 at 08:23:37PM +0300, Benny Halevy wrote:
> > > > Where exactly is the NULL deref?
> > > > 
> > > > > 
> > > > > Note--that's fixed 7 patches later in fsd41: Refactor create_client(),
> > > > > but I don't actually understand how yet.
> > > > 
> > > > unconf's cl_flavor initialization was moved in the latter patch
> > > > from nfsd4_setclientid to create_client so maybe this could
> > > > be the culprit (though, assuming it is initialized to 0
> > > > it will choosing implicitly authnull_ops in rpcauth_create()
> > > > which _should_ work...)
> > > 
> > > Oog, yes, turns out auth_null doesn't initialize the cred hashtable.  So
> > > also reproduceable by mounting with "mount -tnfs4 -osec=null", then
> > > touching a file.  So either we should be using some other interface, or
> > > rpcauth_lookupcred should be checking au_credcache, or something.
> > 
> > There shouldn't be a need for an auth_null hashtable. It isn't a
> > credential...
> 
> Got it.  Looking at the code: I guess rpcauth_lookup_credcache is really
> meant to be used only by auth types implementing their own cred lookups.
> 
> Err, maybe I want the following?
> 
> Or add a "lookup_machine_cred" helper to auth.c.  Or use the
> auth_generic stuff?
> 
> --b.
> 
> diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
> index 77a6d10..b91cc8e 100644
> --- a/fs/nfsd/nfs4callback.c
> +++ b/fs/nfsd/nfs4callback.c
> @@ -450,6 +450,7 @@ static struct rpc_cred *lookup_cb_cred(struct nfs4_cb_conn *cb)
>  	struct auth_cred acred = {
>  		.machine_cred = 1
>  	};
> +	struct rpc_auth *auth = cb->cb_client->cl_auth;
>  
>  	/*
>  	 * Note in the gss case this doesn't actually have to wait for a
> @@ -457,8 +458,7 @@ static struct rpc_cred *lookup_cb_cred(struct nfs4_cb_conn *cb)
>  	 * non-uptodate cred which the rpc state machine will fill in with
>  	 * a refresh_upcall later.
>  	 */
> -	return rpcauth_lookup_credcache(cb->cb_client->cl_auth, &acred,
> -							RPCAUTH_LOOKUP_NEW);
> +	return auth->lookup_cred(auth, &acred, RPCAUTH_LOOKUP_NEW);
>  }
>  
>  void do_probe_callback(struct nfs4_client *clp)

That looks better. There is no guarantee that auth flavours will
implement a credcache...

However, is there any reason why you can't just call
rpc_lookup_machine_cred()?