SUNRPC: Fix a memory leak in the auth credcache code

The leak only affects the RPCSEC_GSS caches, since they are the only ones
that are dynamically allocated...
Rename the existing rpcauth_free_credcache() to rpcauth_clear_credcache()
in order to better describe its role, then add a new function
rpcauth_destroy_credcache() that actually frees the cache in addition to
clearing it out.

Also move the call to destroy the credcache in gss_destroy() to come before
the rpc upcall pipe is unlinked.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

include/linux/sunrpc/auth.h

@@ -143,7 +143,8 @@ int			rpcauth_refreshcred(struct rpc_task *);
 void			rpcauth_invalcred(struct rpc_task *);
 int			rpcauth_uptodatecred(struct rpc_task *);
 int			rpcauth_init_credcache(struct rpc_auth *, unsigned long);
-void			rpcauth_free_credcache(struct rpc_auth *);
+void			rpcauth_destroy_credcache(struct rpc_auth *);
+void			rpcauth_clear_credcache(struct rpc_cred_cache *);
 
 static inline
 struct rpc_cred *	get_rpccred(struct rpc_cred *cred)

net/sunrpc/auth.c

@@ -137,9 +137,8 @@ void rpcauth_destroy_credlist(struct hlist_head *head)
  * that are not referenced.
  */
 void
-rpcauth_free_credcache(struct rpc_auth *auth)
+rpcauth_clear_credcache(struct rpc_cred_cache *cache)
 {
-	struct rpc_cred_cache *cache = auth->au_credcache;
 	HLIST_HEAD(free);
 	struct hlist_node *pos, *next;
 	struct rpc_cred	*cred;
@@ -157,6 +156,21 @@ rpcauth_free_credcache(struct rpc_auth *auth)
 	rpcauth_destroy_credlist(&free);
 }
 
+/*
+ * Destroy the RPC credential cache
+ */
+void
+rpcauth_destroy_credcache(struct rpc_auth *auth)
+{
+	struct rpc_cred_cache *cache = auth->au_credcache;
+
+	if (cache) {
+		auth->au_credcache = NULL;
+		rpcauth_clear_credcache(cache);
+		kfree(cache);
+	}
+}
+
 static void
 rpcauth_prune_expired(struct rpc_auth *auth, struct rpc_cred *cred, struct hlist_head *free)
 {

net/sunrpc/auth_gss/auth_gss.c

@@ -665,12 +665,13 @@ gss_destroy(struct rpc_auth *auth)
 	dprintk("RPC:       destroying GSS authenticator %p flavor %d\n",
 			auth, auth->au_flavor);
 
+	rpcauth_destroy_credcache(auth);
+
 	gss_auth = container_of(auth, struct gss_auth, rpc_auth);
 	rpc_unlink(gss_auth->dentry);
 	gss_auth->dentry = NULL;
 	gss_mech_put(gss_auth->mech);
 
-	rpcauth_free_credcache(auth);
 	kfree(gss_auth);
 	module_put(THIS_MODULE);
 }

net/sunrpc/auth_unix.c

@@ -50,7 +50,7 @@ static void
 unx_destroy(struct rpc_auth *auth)
 {
 	dprintk("RPC:       destroying UNIX authenticator %p\n", auth);
-	rpcauth_free_credcache(auth);
+	rpcauth_clear_credcache(auth->au_credcache);
 }
 
 /*

net/sunrpc/sunrpc_syms.c

@@ -57,7 +57,7 @@ EXPORT_SYMBOL(rpcauth_unregister);
 EXPORT_SYMBOL(rpcauth_create);
 EXPORT_SYMBOL(rpcauth_lookupcred);
 EXPORT_SYMBOL(rpcauth_lookup_credcache);
-EXPORT_SYMBOL(rpcauth_free_credcache);
+EXPORT_SYMBOL(rpcauth_destroy_credcache);
 EXPORT_SYMBOL(rpcauth_init_credcache);
 EXPORT_SYMBOL(put_rpccred);