NFS/SUNRPC: don't lookup machine credential until rpcauth_bindcred().

When NFS creates a machine credential, it is a "generic" credential,
not tied to any auth protocol, and is really just a container for
the princpal name.
This doesn't get linked to a genuine credential until rpcauth_bindcred()
is called.
The lookup always succeeds, so various places that test if the machine
credential is NULL, are pointless.

As a step towards getting rid of generic credentials, this patch gets
rid of generic machine credentials.  The nfs_client and rpc_client
just hold a pointer to a constant principal name.
When a machine credential is wanted, a special static 'struct rpc_cred'
pointer is used. rpcauth_bindcred() recognizes this, finds the
principal from the client, and binds the correct credential.

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

1 files changed, 4 insertions, 8 deletions

diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
index c032e4c24a8d..1dcee1fd32d9 100644
--- a/fs/nfsd/nfs4callback.c
+++ b/fs/nfsd/nfs4callback.c
@@ -847,14 +847,10 @@ static int max_cb_time(struct net *net)
 static struct rpc_cred *get_backchannel_cred(struct nfs4_client *clp, struct rpc_clnt *client, struct nfsd4_session *ses)
 {
         if (clp->cl_minorversion == 0) {
-                char *principal = clp->cl_cred.cr_targ_princ ?
-                                        clp->cl_cred.cr_targ_princ : "nfs";
-                struct rpc_cred *cred;
-
-                cred = rpc_lookup_machine_cred(principal);
-                if (!IS_ERR(cred))
-                        get_rpccred(cred);
-                return cred;
+                client->cl_principal = clp->cl_cred.cr_targ_princ ?
+                        clp->cl_cred.cr_targ_princ : "nfs";
+
+                return get_rpccred(rpc_machine_cred());
         } else {
                 struct rpc_auth *auth = client->cl_auth;
                 struct auth_cred acred = {};