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>

3 files changed, 7 insertions, 34 deletions

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index cce151776709..fb1cf1a4bda2 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -151,7 +151,6 @@ EXPORT_SYMBOL_GPL(unregister_nfs_version);
 struct nfs_client *nfs_alloc_client(const struct nfs_client_initdata *cl_init)
 {
 	struct nfs_client *clp;
-	struct rpc_cred *cred;
 	int err = -ENOMEM;
 
 	if ((clp = kzalloc(sizeof(*clp), GFP_KERNEL)) == NULL)
@@ -182,9 +181,7 @@ struct nfs_client *nfs_alloc_client(const struct nfs_client_initdata *cl_init)
 	clp->cl_proto = cl_init->proto;
 	clp->cl_net = get_net(cl_init->net);
 
-	cred = rpc_lookup_machine_cred("*");
-	if (!IS_ERR(cred))
-		clp->cl_machine_cred = cred;
+	clp->cl_principal = "*";
 	nfs_fscache_get_client_cookie(clp);
 
 	return clp;
@@ -246,11 +243,6 @@ void nfs_free_client(struct nfs_client *clp)
 	if (!IS_ERR(clp->cl_rpcclient))
 		rpc_shutdown_client(clp->cl_rpcclient);
 
-	if (clp->cl_machine_cred != NULL)
-		put_rpccred(clp->cl_machine_cred);
-	if (clp->cl_root_cred != NULL)
-		put_rpccred(clp->cl_root_cred);
-
 	put_net(clp->cl_net);
 	put_nfs_version(clp->cl_nfs_mod);
 	kfree(clp->cl_hostname);
@@ -529,6 +521,7 @@ int nfs_create_rpc_client(struct nfs_client *clp,
 		return PTR_ERR(clnt);
 	}
 
+	clnt->cl_principal = clp->cl_principal;
 	clp->cl_rpcclient = clnt;
 	return 0;
 }
diff --git a/fs/nfs/nfs4_fs.h b/fs/nfs/nfs4_fs.h
index ad649a49822f..eab41490ce58 100644
--- a/fs/nfs/nfs4_fs.h
+++ b/fs/nfs/nfs4_fs.h
@@ -338,7 +338,6 @@ static inline bool
 _nfs4_state_protect(struct nfs_client *clp, unsigned long sp4_mode,
 		    struct rpc_clnt **clntp, struct rpc_message *msg)
 {
-	struct rpc_cred *newcred = NULL;
 	rpc_authflavor_t flavor;
 
 	if (sp4_mode == NFS_SP4_MACH_CRED_CLEANUP ||
@@ -353,13 +352,7 @@ _nfs4_state_protect(struct nfs_client *clp, unsigned long sp4_mode,
 			return false;
 	}
 	if (test_bit(sp4_mode, &clp->cl_sp4_flags)) {
-		spin_lock(&clp->cl_lock);
-		if (clp->cl_machine_cred != NULL)
-			/* don't call get_rpccred on the machine cred -
-			 * a reference will be held for life of clp */
-			newcred = clp->cl_machine_cred;
-		spin_unlock(&clp->cl_lock);
-		msg->rpc_cred = newcred;
+		msg->rpc_cred = rpc_machine_cred();
 
 		flavor = clp->cl_rpcclient->cl_auth->au_flavor;
 		WARN_ON_ONCE(flavor != RPC_AUTH_GSS_KRB5I &&
diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index f142fca6995b..6304c79dbcd1 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -166,28 +166,15 @@ out:
 
 struct rpc_cred *nfs4_get_machine_cred(struct nfs_client *clp)
 {
-	struct rpc_cred *cred = clp->cl_root_cred;
-
-	if (!cred)
-		cred = clp->cl_machine_cred;
-	if (cred)
-		return get_rpccred(cred);
-	return cred;
+	return get_rpccred(rpc_machine_cred());
 }
 
 static void nfs4_root_machine_cred(struct nfs_client *clp)
 {
-	struct rpc_cred *new;
 
-	new = rpc_lookup_machine_cred(NULL);
-	spin_lock(&clp->cl_lock);
-	if (clp->cl_root_cred == NULL) {
-		clp->cl_root_cred = new;
-		new = NULL;
-	}
-	spin_unlock(&clp->cl_lock);
-	if (new != NULL)
-		put_rpccred(new);
+	/* Force root creds instead of machine */
+	clp->cl_principal = NULL;
+	clp->cl_rpcclient->cl_principal = NULL;
 }
 
 static struct rpc_cred *