/*
* fs/nfs/idmap.c
*
* UID and GID to name mapping for clients.
*
* Copyright (c) 2002 The Regents of the University of Michigan.
* All rights reserved.
*
* Marius Aamodt Eriksen <[email protected]>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
* BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <linux/types.h>
#include <linux/parser.h>
#include <linux/fs.h>
#include <net/net_namespace.h>
#include <linux/sunrpc/rpc_pipe_fs.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_fs_sb.h>
#include <linux/key.h>
#include <linux/keyctl.h>
#include <linux/key-type.h>
#include <keys/user-type.h>
#include <keys/request_key_auth-type.h>
#include <linux/module.h>
#include <linux/user_namespace.h>
#include "internal.h"
#include "netns.h"
#include "nfs4idmap.h"
#include "nfs4trace.h"
#define NFS_UINT_MAXLEN 11
static const struct cred *id_resolver_cache;
static struct key_type key_type_id_resolver_legacy;
struct idmap_legacy_upcalldata {
struct rpc_pipe_msg pipe_msg;
struct idmap_msg idmap_msg;
struct key *authkey;
struct idmap *idmap;
};
struct idmap {
struct rpc_pipe_dir_object idmap_pdo;
struct rpc_pipe *idmap_pipe;
struct idmap_legacy_upcalldata *idmap_upcall_data;
struct mutex idmap_mutex;
struct user_namespace *user_ns;
};
static struct user_namespace *idmap_userns(const struct idmap *idmap)
{
if (idmap && idmap->user_ns)
return idmap->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
* @owner_name: owner name string cache
* @group_name: group name string cache
*/
void nfs_fattr_init_names(struct nfs_fattr *fattr,
struct nfs4_string *owner_name,
struct nfs4_string *group_name)
{
fattr->owner_name = owner_name;
fattr->group_name = group_name;
}
static void nfs_fattr_free_owner_name(struct nfs_fattr *fattr)
{
fattr->valid &= ~NFS_ATTR_FATTR_OWNER_NAME;
kfree(fattr->owner_name->data);
}
static void nfs_fattr_free_group_name(struct nfs_fattr *fattr)
{
fattr->valid &= ~NFS_ATTR_FATTR_GROUP_NAME;
kfree(fattr->group_name->data);
}
static bool nfs_fattr_map_owner_name(struct nfs_server *server, struct nfs_fattr *fattr)
{
struct nfs4_string *owner = fattr->owner_name;
kuid_t uid;
if (!(fattr->valid & NFS_ATTR_FATTR_OWNER_NAME))
return false;
if (nfs_map_name_to_uid(server, owner->data, owner->len, &uid) == 0) {
fattr->uid = uid;
fattr->valid |= NFS_ATTR_FATTR_OWNER;
}
return true;
}
static bool nfs_fattr_map_group_name(struct nfs_server *server, struct nfs_fattr *fattr)
{
struct nfs4_string *group = fattr->group_name;
kgid_t gid;
if (!(fattr->valid & NFS_ATTR_FATTR_GROUP_NAME))
return false;
if (nfs_map_group_to_gid(server, group->data, group->len, &gid) == 0) {
fattr->gid = gid;
fattr->valid |= NFS_ATTR_FATTR_GROUP;
}
return true;
}
/**
* nfs_fattr_free_names - free up the NFSv4 owner and group strings
* @fattr: a fully initialised nfs_fattr structure
*/
void nfs_fattr_free_names(struct nfs_fattr *fattr)
{
if (fattr->valid & NFS_ATTR_FATTR_OWNER_NAME)
nfs_fattr_free_owner_name(fattr);
if (fattr->valid & NFS_ATTR_FATTR_GROUP_NAME)
nfs_fattr_free_group_name(fattr);
}
/**
* nfs_fattr_map_and_free_names - map owner/group strings into uid/gid and free
* @server: pointer to the filesystem nfs_server structure
* @fattr: a fully initialised nfs_fattr structure
*
* This helper maps the cached NFSv4 owner/group strings in fattr into
* their numeric uid/gid equivalents, and then frees the cached strings.
*/
void nfs_fattr_map_and_free_names(struct nfs_server *server, struct nfs_fattr *fattr)
{
if (nfs_fattr_map_owner_name(server, fattr))
nfs_fattr_free_owner_name(fattr);
if (nfs_fattr_map_group_name(server, fattr))
nfs_fattr_free_group_name(fattr);
}
int nfs_map_string_to_numeric(const char *name, size_t namelen, __u32 *res)
{
unsigned long val;
char buf[16];
if (memchr(name, '@', namelen) != NULL || namelen >= sizeof(buf))
return 0;
memcpy(buf, name, namelen);
buf[namelen] = '\0';
if (kstrtoul(buf, 0, &val) != 0)
return 0;
*res = val;
return 1;
}
EXPORT_SYMBOL_GPL(nfs_map_string_to_numeric);
static int nfs_map_numeric_to_string(__u32 id, char *buf, size_t buflen)
{
return snprintf(buf, buflen, "%u", id);
}
static struct key_type key_type_id_resolver = {
.name = "id_resolver",
.preparse = user_preparse,
.free_preparse = user_free_preparse,
.instantiate = generic_key_instantiate,
.revoke = user_revoke,
.destroy = user_destroy,
.describe = user_describe,
.read = user_read,
};
int nfs_idmap_init(void)
{
struct cred *cred;
struct key *keyring;
int ret = 0;
printk(KERN_NOTICE "NFS: Registering the %s key type\n",
key_type_id_resolver.name);
cred = prepare_kernel_cred(&init_task);
if (!cred)
return -ENOMEM;
keyring = keyring_alloc(".id_resolver",
GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, cred,
(KEY_POS_ALL & ~KEY_POS_SETATTR) |
KEY_USR_VIEW | KEY_USR_READ,
KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
if (IS_ERR(keyring)) {
ret = PTR_ERR(keyring);
goto failed_put_cred;
}
ret = register_key_type(&key_type_id_resolver);
if (ret < 0)
goto failed_put_key;
ret = register_key_type(&key_type_id_resolver_legacy);
if (ret < 0)
goto failed_reg_legacy;
set_bit(KEY_FLAG_ROOT_CAN_CLEAR, &keyring->flags);
cred->thread_keyring = keyring;
cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
id_resolver_cache = cred;
return 0;
failed_reg_legacy:
unregister_key_type(&key_type_id_resolver);
failed_put_key:
key_put(keyring);
failed_put_cred:
put_cred(cred);
return ret;
}
void nfs_idmap_quit(void)
{
key_revoke(id_resolver_cache->thread_keyring);
unregister_key_type(&key_type_id_resolver);
unregister_key_type(&key_type_id_resolver_legacy);
put_cred(id_resolver_cache);
}
/*
* Assemble the description to pass to request_key()
* This function will allocate a new string and update dest to point
* at it. The caller is responsible for freeing dest.
*
* On error 0 is returned. Otherwise, the length of dest is returned.
*/
static ssize_t nfs_idmap_get_desc(const char *name, size_t namelen,
const char *type, size_t typelen, char **desc)
{
char *cp;
size_t desclen = typelen + namelen + 2;
*desc = kmalloc(desclen, GFP_KERNEL);
if (!*desc)
return -ENOMEM;
cp = *desc;
memcpy(cp, type, typelen);
cp += typelen;
*cp++ = ':';
memcpy(cp, name, namelen);
cp += namelen;
*cp = '\0';
return desclen;
}
static struct key *nfs_idmap_request_key(const char *name, size_t namelen,
const char *type, struct idmap *idmap)
{
char *desc;
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);
if (!idmap->user_ns || idmap->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,
desc, NULL, "", 0, idmap);
mutex_unlock(&idmap->idmap_mutex);
}
if (!IS_ERR(rkey))
set_bit(KEY_FLAG_ROOT_CAN_INVAL, &rkey->flags);
kfree(desc);
return rkey;
}
static ssize_t nfs_idmap_get_key(const char *name, size_t namelen,
const char *type, void *data,
size_t data_size, struct idmap *idmap)
{
const struct cred *saved_cred;
struct key *rkey;
const struct user_key_payload *payload;
ssize_t ret;
saved_cred = override_creds(id_resolver_cache);
rkey = nfs_idmap_request_key(name, namelen, type, idmap);
revert_creds(saved_cred);
if (IS_ERR(rkey)) {
ret = PTR_ERR(rkey);
goto out;
}
rcu_read_lock();
rkey->perm |= KEY_USR_VIEW;
ret = key_validate(rkey);
if (ret < 0)
goto out_up;
payload = user_key_payload_rcu(rkey);
if (IS_ERR_OR_NULL(payload)) {
ret = PTR_ERR(payload);
goto out_up;
}
ret = payload->datalen;
if (ret > 0 && ret <= data_size)
memcpy(data, payload->data, ret);
else
ret = -EINVAL;
out_up:
rcu_read_unlock();
key_put(rkey);
out:
return ret;
}
/* ID -> Name */
static ssize_t nfs_idmap_lookup_name(__u32 id, const char *type, char *buf,
size_t buflen, struct idmap *idmap)
{
char id_str[NFS_UINT_MAXLEN];
int id_len;
ssize_t ret;
id_len = nfs_map_numeric_to_string(id, id_str, sizeof(id_str));
ret = nfs_idmap_get_key(id_str, id_len, type, buf, buflen, idmap);
if (ret < 0)
return -EINVAL;
return ret;
}
/* Name -> ID */
static int nfs_idmap_lookup_id(const char *name, size_t namelen, const char *type,
__u32 *id, struct idmap *idmap)
{
char id_str[NFS_UINT_MAXLEN];
long id_long;
ssize_t data_size;
int ret = 0;
data_size = nfs_idmap_get_key(name, namelen, type, id_str, NFS_UINT_MAXLEN, idmap);
if (data_size <= 0) {
ret = -EINVAL;
} else {
ret = kstrtol(id_str, 10, &id_long);
if (!ret)
*id = (__u32)id_long;
}
return ret;
}
/* idmap classic begins here */
enum {
Opt_find_uid, Opt_find_gid, Opt_find_user, Opt_find_group, Opt_find_err
};
static const match_table_t nfs_idmap_tokens = {
{ Opt_find_uid, "uid:%s" },
{ Opt_find_gid, "gid:%s" },
{ Opt_find_user, "user:%s" },
{ Opt_find_group, "group:%s" },
{ Opt_find_err, NULL }
};
static int nfs_idmap_legacy_upcall(struct key *, void *);
static ssize_t idmap_pipe_downcall(struct file *, const char __user *,
size_t);
static void idmap_release_pipe(struct inode *);
static void idmap_pipe_destroy_msg(struct rpc_pipe_msg *);
static const struct rpc_pipe_ops idmap_upcall_ops = {
.upcall = rpc_pipe_generic_upcall,
.downcall = idmap_pipe_downcall,
.release_pipe = idmap_release_pipe,
.destroy_msg = idmap_pipe_destroy_msg,
};
static struct key_type key_type_id_resolver_legacy = {
.name = "id_legacy",
.preparse = user_preparse,
.free_preparse = user_free_preparse,
.instantiate = generic_key_instantiate,
.revoke = user_revoke,
.destroy = user_destroy,
.describe = user_describe,
.read = user_read,
.request_key = nfs_idmap_legacy_upcall,
};
static void nfs_idmap_pipe_destroy(struct dentry *dir,
struct rpc_pipe_dir_object *pdo)
{
struct idmap *idmap = pdo->pdo_data;
struct rpc_pipe *pipe = idmap->idmap_pipe;
if (pipe->dentry) {
rpc_unlink(pipe->dentry);
pipe->dentry = NULL;
}
}
static int nfs_idmap_pipe_create(struct dentry *dir,
struct rpc_pipe_dir_object *pdo)
{
struct idmap *idmap = pdo->pdo_data;
struct rpc_pipe *pipe = idmap->idmap_pipe;
struct dentry *dentry;
dentry = rpc_mkpipe_dentry(dir, "idmap", idmap, pipe);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
pipe->dentry = dentry;
return 0;
}
static const struct rpc_pipe_dir_object_ops nfs_idmap_pipe_dir_object_ops = {
.create = nfs_idmap_pipe_create,
.destroy = nfs_idmap_pipe_destroy,
};
int
nfs_idmap_new(struct nfs_client *clp)
{
struct idmap *idmap;
struct rpc_pipe *pipe;
int error;
idmap = kzalloc(sizeof(*idmap), GFP_KERNEL);
if (idmap == NULL)
return -ENOMEM;
mutex_init(&idmap->idmap_mutex);
idmap->user_ns = get_user_ns(clp->cl_rpcclient->cl_cred->user_ns);
rpc_init_pipe_dir_object(&idmap->idmap_pdo,
&nfs_idmap_pipe_dir_object_ops,
idmap);
pipe = rpc_mkpipe_data(&idmap_upcall_ops, 0);
if (IS_ERR(pipe)) {
error = PTR_ERR(pipe);
goto err;
}
idmap->idmap_pipe = pipe;
error = rpc_add_pipe_dir_object(clp->cl_net,
&clp->cl_rpcclient->cl_pipedir_objects,
&idmap->idmap_pdo);
if (error)
goto err_destroy_pipe;
clp->cl_idmap = idmap;
return 0;
err_destroy_pipe:
rpc_destroy_pipe_data(idmap->idmap_pipe);
err:
put_user_ns(idmap->user_ns);
kfree(idmap);
return error;
}
void
nfs_idmap_delete(struct nfs_client *clp)
{
struct idmap *idmap = clp->cl_idmap;
if (!idmap)
return;
clp->cl_idmap = NULL;
rpc_remove_pipe_dir_object(clp->cl_net,
&clp->cl_rpcclient->cl_pipedir_objects,
&idmap->idmap_pdo);
rpc_destroy_pipe_data(idmap->idmap_pipe);
put_user_ns(idmap->user_ns);
kfree(idmap);
}
static int nfs_idmap_prepare_message(char *desc, struct idmap *idmap,
struct idmap_msg *im,
struct rpc_pipe_msg *msg)
{
substring_t substr;
int token, ret;
im->im_type = IDMAP_TYPE_GROUP;
token = match_token(desc, nfs_idmap_tokens, &substr);
switch (token) {
case Opt_find_uid:
im->im_type = IDMAP_TYPE_USER;
fallthrough;
case Opt_find_gid:
im->im_conv = IDMAP_CONV_NAMETOID;
ret = match_strlcpy(im->im_name, &substr, IDMAP_NAMESZ);
break;
case Opt_find_user:
im->im_type = IDMAP_TYPE_USER;
fallthrough;
case Opt_find_group:
im->im_conv = IDMAP_CONV_IDTONAME;
ret = match_int(&substr, &im->im_id);
if (ret)
goto out;
break;
default:
ret = -EINVAL;
goto out;
}
msg->data = im;
msg->len = sizeof(struct idmap_msg);
out:
return ret;
}
static bool
nfs_idmap_prepare_pipe_upcall(struct idmap *idmap,
struct idmap_legacy_upcalldata *data)
{
if (idmap->idmap_upcall_data != NULL) {
WARN_ON_ONCE(1);
return false;
}
idmap->idmap_upcall_data = data;
return true;
}
static void nfs_idmap_complete_pipe_upcall(struct idmap_legacy_upcalldata *data,
int ret)
{
complete_request_key(data->authkey, ret);
key_put(data->authkey);
kfree(data);
}
static void nfs_idmap_abort_pipe_upcall(struct idmap *idmap,
struct idmap_legacy_upcalldata *data,
int ret)
{
if (cmpxchg(&idmap->idmap_upcall_data, data, NULL) == data)
nfs_idmap_complete_pipe_upcall(data, ret);
}
static int nfs_idmap_legacy_upcall(struct key *authkey, void *aux)
{
struct idmap_legacy_upcalldata *data;
struct request_key_auth *rka = get_request_key_auth(authkey);
struct rpc_pipe_msg *msg;
struct idmap_msg *im;
struct idmap *idmap = aux;
struct key *key = rka->target_key;
int ret = -ENOKEY;
if (!aux)
goto out1;
/* msg and im are freed in idmap_pipe_destroy_msg */
ret = -ENOMEM;
data = kzalloc(sizeof(*data), GFP_KERNEL);
if (!data)
goto out1;
msg = &data->pipe_msg;
im = &data->idmap_msg;
data->idmap = idmap;
data->authkey = key_get(authkey);
ret = nfs_idmap_prepare_message(key->description, idmap, im, msg);
if (ret < 0)
goto out2;
ret = -EAGAIN;
if (!nfs_idmap_prepare_pipe_upcall(idmap, data))
goto out2;
ret = rpc_queue_upcall(idmap->idmap_pipe, msg);
if (ret < 0)
nfs_idmap_abort_pipe_upcall(idmap, data, ret);
return ret;
out2:
kfree(data);
out1:
complete_request_key(authkey, ret);
return ret;
}
static int nfs_idmap_instantiate(struct key *key, struct key *authkey, char *data, size_t datalen)
{
return key_instantiate_and_link(key, data, datalen,
id_resolver_cache->thread_keyring,
authkey);
}
static int nfs_idmap_read_and_verify_message(struct idmap_msg *im,
struct idmap_msg *upcall,
struct key *key, struct key *authkey)
{
char id_str[NFS_UINT_MAXLEN];
size_t len;
int ret = -ENOKEY;
/* ret = -ENOKEY */
if (upcall->im_type != im->im_type || upcall->im_conv != im->im_conv)
goto out;
switch (im->im_conv) {
case IDMAP_CONV_NAMETOID:
if (strcmp(upcall->im_name, im->im_name) != 0)
break;
/* Note: here we store the NUL terminator too */
len = 1 + nfs_map_numeric_to_string(im->im_id, id_str,
sizeof(id_str));
ret = nfs_idmap_instantiate(key, authkey, id_str, len);
break;
case IDMAP_CONV_IDTONAME:
if (upcall->im_id != im->im_id)
break;
len = strlen(im->im_name);
ret = nfs_idmap_instantiate(key, authkey, im->im_name, len);
break;
default:
ret = -EINVAL;
}
out:
return ret;
}
static ssize_t
idmap_pipe_downcall(struct file *filp, const char __user *src, size_t mlen)
{
struct request_key_auth *rka;
struct rpc_inode *rpci = RPC_I(file_inode(filp));
struct idmap *idmap = (struct idmap *)rpci->private;
struct idmap_legacy_upcalldata *data;
struct key *authkey;
struct idmap_msg im;
size_t namelen_in;
int ret = -ENOKEY;
/* If instantiation is successful, anyone waiting for key construction
* will have been woken up and someone else may now have used
* idmap_key_cons - so after this point we may no longer touch it.
*/
data = xchg(&idmap->idmap_upcall_data, NULL);
if (data == NULL)
goto out_noupcall;
authkey = data->authkey;
rka = get_request_key_auth(authkey);
if (mlen != sizeof(im)) {
ret = -ENOSPC;
goto out;
}
if (copy_from_user(&im, src, mlen) != 0) {
ret = -EFAULT;
goto out;
}
if (!(im.im_status & IDMAP_STATUS_SUCCESS)) {
ret = -ENOKEY;
goto out;
}
namelen_in = strnlen(im.im_name, IDMAP_NAMESZ);
if (namelen_in == 0 || namelen_in == IDMAP_NAMESZ) {
ret = -EINVAL;
goto out;
}
ret = nfs_idmap_read_and_verify_message(&im, &data->idmap_msg,
rka->target_key, authkey);
if (ret >= 0) {
key_set_timeout(rka->target_key, nfs_idmap_cache_timeout);
ret = mlen;
}
out:
nfs_idmap_complete_pipe_upcall(data, ret);
out_noupcall:
return ret;
}
static void
idmap_pipe_destroy_msg(struct rpc_pipe_msg *msg)
{
struct idmap_legacy_upcalldata *data = container_of(msg,
struct idmap_legacy_upcalldata,
pipe_msg);
struct idmap *idmap = data->idmap;
if (msg->errno)
nfs_idmap_abort_pipe_upcall(idmap, data, msg->errno);
}
static void
idmap_release_pipe(struct inode *inode)
{
struct rpc_inode *rpci = RPC_I(inode);
struct idmap *idmap = (struct idmap *)rpci->private;
struct idmap_legacy_upcalldata *data;
data = xchg(&idmap->idmap_upcall_data, NULL);
if (data)
nfs_idmap_complete_pipe_upcall(data, -EPIPE);
}
int nfs_map_name_to_uid(const struct nfs_server *server, const char *name, size_t namelen, kuid_t *uid)
{
struct idmap *idmap = server->nfs_client->cl_idmap;
__u32 id = -1;
int ret = 0;
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(idmap_userns(idmap), id);
if (!uid_valid(*uid))
ret = -ERANGE;
}
trace_nfs4_map_name_to_uid(name, namelen, id, ret);
return ret;
}
int nfs_map_group_to_gid(const struct nfs_server *server, const char *name, size_t namelen, kgid_t *gid)
{
struct idmap *idmap = server->nfs_client->cl_idmap;
__u32 id = -1;
int ret = 0;
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(idmap_userns(idmap), id);
if (!gid_valid(*gid))
ret = -ERANGE;
}
trace_nfs4_map_group_to_gid(name, namelen, id, ret);
return ret;
}
int nfs_map_uid_to_name(const struct nfs_server *server, kuid_t uid, char *buf, size_t buflen)
{
struct idmap *idmap = server->nfs_client->cl_idmap;
int ret = -EINVAL;
__u32 id;
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)
ret = nfs_map_numeric_to_string(id, buf, buflen);
trace_nfs4_map_uid_to_name(buf, ret, id, ret);
return ret;
}
int nfs_map_gid_to_group(const struct nfs_server *server, kgid_t gid, char *buf, size_t buflen)
{
struct idmap *idmap = server->nfs_client->cl_idmap;
int ret = -EINVAL;
__u32 id;
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)
ret = nfs_map_numeric_to_string(id, buf, buflen);
trace_nfs4_map_gid_to_group(buf, ret, id, ret);
return ret;
}
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