NFSv4: Convert the NFS client idmapper to use the container user namespace

When mapping NFS identities using the NFSv4 idmapper, we want to substitute
for the uids and gids that would normally go on the wire as part of a
NFSv3 request. So we use the same mapping in the NFSv4 upcall as we
use in the NFSv3 RPC call (i.e. the mapping stored in the rpc_clnt cred).
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

fs/nfs/nfs4idmap.c

@@ -69,8 +69,16 @@ struct idmap {
 	struct rpc_pipe		*idmap_pipe;
 	struct idmap_legacy_upcalldata *idmap_upcall_data;
 	struct mutex		idmap_mutex;
+	const struct cred	*cred;
 };
 
+static struct user_namespace *idmap_userns(const struct idmap *idmap)
+{
+	if (idmap && idmap->cred)
+		return idmap->cred->user_ns;
+	return &init_user_ns;
+}
+
 /**
  * nfs_fattr_init_names - initialise the nfs_fattr owner_name/group_name fields
  * @fattr: fully initialised struct nfs_fattr
@@ -271,14 +279,15 @@ static struct key *nfs_idmap_request_key(const char *name, size_t namelen,
 					 const char *type, struct idmap *idmap)
 {
 	char *desc;
-	struct key *rkey;
+	struct key *rkey = ERR_PTR(-EAGAIN);
 	ssize_t ret;
 
 	ret = nfs_idmap_get_desc(name, namelen, type, strlen(type), &desc);
 	if (ret < 0)
 		return ERR_PTR(ret);
 
-	rkey = request_key(&key_type_id_resolver, desc, "");
+	if (!idmap->cred || idmap->cred->user_ns == &init_user_ns)
+		rkey = request_key(&key_type_id_resolver, desc, "");
 	if (IS_ERR(rkey)) {
 		mutex_lock(&idmap->idmap_mutex);
 		rkey = request_key_with_auxdata(&key_type_id_resolver_legacy,
@@ -452,6 +461,9 @@ nfs_idmap_new(struct nfs_client *clp)
 	if (idmap == NULL)
 		return -ENOMEM;
 
+	mutex_init(&idmap->idmap_mutex);
+	idmap->cred = get_cred(clp->cl_rpcclient->cl_cred);
+
 	rpc_init_pipe_dir_object(&idmap->idmap_pdo,
 			&nfs_idmap_pipe_dir_object_ops,
 			idmap);
@@ -462,7 +474,6 @@ nfs_idmap_new(struct nfs_client *clp)
 		goto err;
 	}
 	idmap->idmap_pipe = pipe;
-	mutex_init(&idmap->idmap_mutex);
 
 	error = rpc_add_pipe_dir_object(clp->cl_net,
 			&clp->cl_rpcclient->cl_pipedir_objects,
@@ -475,6 +486,7 @@ nfs_idmap_new(struct nfs_client *clp)
 err_destroy_pipe:
 	rpc_destroy_pipe_data(idmap->idmap_pipe);
 err:
+	put_cred(idmap->cred);
 	kfree(idmap);
 	return error;
 }
@@ -491,6 +503,7 @@ nfs_idmap_delete(struct nfs_client *clp)
 			&clp->cl_rpcclient->cl_pipedir_objects,
 			&idmap->idmap_pdo);
 	rpc_destroy_pipe_data(idmap->idmap_pipe);
+	put_cred(idmap->cred);
 	kfree(idmap);
 }
 
@@ -735,7 +748,7 @@ int nfs_map_name_to_uid(const struct nfs_server *server, const char *name, size_
 	if (!nfs_map_string_to_numeric(name, namelen, &id))
 		ret = nfs_idmap_lookup_id(name, namelen, "uid", &id, idmap);
 	if (ret == 0) {
-		*uid = make_kuid(&init_user_ns, id);
+		*uid = make_kuid(idmap_userns(idmap), id);
 		if (!uid_valid(*uid))
 			ret = -ERANGE;
 	}
@@ -752,7 +765,7 @@ int nfs_map_group_to_gid(const struct nfs_server *server, const char *name, size
 	if (!nfs_map_string_to_numeric(name, namelen, &id))
 		ret = nfs_idmap_lookup_id(name, namelen, "gid", &id, idmap);
 	if (ret == 0) {
-		*gid = make_kgid(&init_user_ns, id);
+		*gid = make_kgid(idmap_userns(idmap), id);
 		if (!gid_valid(*gid))
 			ret = -ERANGE;
 	}
@@ -766,7 +779,7 @@ int nfs_map_uid_to_name(const struct nfs_server *server, kuid_t uid, char *buf,
 	int ret = -EINVAL;
 	__u32 id;
 
-	id = from_kuid(&init_user_ns, uid);
+	id = from_kuid_munged(idmap_userns(idmap), uid);
 	if (!(server->caps & NFS_CAP_UIDGID_NOMAP))
 		ret = nfs_idmap_lookup_name(id, "user", buf, buflen, idmap);
 	if (ret < 0)
@@ -780,7 +793,7 @@ int nfs_map_gid_to_group(const struct nfs_server *server, kgid_t gid, char *buf,
 	int ret = -EINVAL;
 	__u32 id;
 
-	id = from_kgid(&init_user_ns, gid);
+	id = from_kgid_munged(idmap_userns(idmap), gid);
 	if (!(server->caps & NFS_CAP_UIDGID_NOMAP))
 		ret = nfs_idmap_lookup_name(id, "group", buf, buflen, idmap);
 	if (ret < 0)