SUNRPC: Introduce rpc_clone_client_set_auth()

An ULP is supposed to be able to replace a GSS rpc_auth object with
another GSS rpc_auth object using rpcauth_create().  However,
rpcauth_create() in 3.5 reliably fails with -EEXIST in this case.
This is because when gss_create() attempts to create the upcall pipes,
sometimes they are already there.  For example if a pipe FS mount
event occurs, or a previous GSS flavor was in use for this rpc_clnt.

It turns out that's not the only problem here.  While working on a
fix for the above problem, we noticed that replacing an rpc_clnt's
rpc_auth is not safe, since dereferencing the cl_auth field is not
protected in any way.

So we're deprecating the ability of rpcauth_create() to switch an
rpc_clnt's security flavor during normal operation.  Instead, let's
add a fresh API that clones an rpc_clnt and gives the clone a new
flavor before it's used.

This makes immediate use of the new __rpc_clone_client() helper.

This can be used in a similar fashion to rpcauth_create() when a
client is hunting for the correct security flavor.  Instead of
replacing an rpc_clnt's security flavor in a loop, the ULP replaces
the whole rpc_clnt.

To fix the -EEXIST problem, any ULP logic that relies on replacing
an rpc_clnt's rpc_auth with rpcauth_create() must be changed to use
this API instead.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 2 insertions, 11 deletions

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 99694442b93f..143149db3440 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -668,7 +668,8 @@ int nfs_init_server_rpcclient(struct nfs_server *server,
 {
         struct nfs_client *clp = server->nfs_client;
 
-        server->client = rpc_clone_client(clp->cl_rpcclient);
+        server->client = rpc_clone_client_set_auth(clp->cl_rpcclient,
+                                                        pseudoflavour);
         if (IS_ERR(server->client)) {
                 dprintk("%s: couldn't create rpc_client!\n", __func__);
                 return PTR_ERR(server->client);
@@ -678,16 +679,6 @@ int nfs_init_server_rpcclient(struct nfs_server *server,
                         timeo,
                         sizeof(server->client->cl_timeout_default));
         server->client->cl_timeout = &server->client->cl_timeout_default;
-
-        if (pseudoflavour != clp->cl_rpcclient->cl_auth->au_flavor) {
-                struct rpc_auth *auth;
-
-                auth = rpcauth_create(pseudoflavour, server->client);
-                if (IS_ERR(auth)) {
-                        dprintk("%s: couldn't create credcache!\n", __func__);
-                        return PTR_ERR(auth);
-                }
-        }
         server->client->cl_softrtry = 0;
         if (server->flags & NFS_MOUNT_SOFT)
                 server->client->cl_softrtry = 1;