- 根目录:
- fs
- ubifs
- xattr.c
/*
* This file is part of UBIFS.
*
* Copyright (C) 2006-2008 Nokia Corporation.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 as published by
* the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
* You should have received a copy of the GNU General Public License along with
* this program; if not, write to the Free Software Foundation, Inc., 51
* Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*
* Authors: Artem Bityutskiy (Битюцкий Артём)
* Adrian Hunter
*/
/*
* This file implements UBIFS extended attributes support.
*
* Extended attributes are implemented as regular inodes with attached data,
* which limits extended attribute size to UBIFS block size (4KiB). Names of
* extended attributes are described by extended attribute entries (xentries),
* which are almost identical to directory entries, but have different key type.
*
* In other words, the situation with extended attributes is very similar to
* directories. Indeed, any inode (but of course not xattr inodes) may have a
* number of associated xentries, just like directory inodes have associated
* directory entries. Extended attribute entries store the name of the extended
* attribute, the host inode number, and the extended attribute inode number.
* Similarly, direntries store the name, the parent and the target inode
* numbers. Thus, most of the common UBIFS mechanisms may be re-used for
* extended attributes.
*
* The number of extended attributes is not limited, but there is Linux
* limitation on the maximum possible size of the list of all extended
* attributes associated with an inode (%XATTR_LIST_MAX), so UBIFS makes sure
* the sum of all extended attribute names of the inode does not exceed that
* limit.
*
* Extended attributes are synchronous, which means they are written to the
* flash media synchronously and there is no write-back for extended attribute
* inodes. The extended attribute values are not stored in compressed form on
* the media.
*
* Since extended attributes are represented by regular inodes, they are cached
* in the VFS inode cache. The xentries are cached in the LNC cache (see
* tnc.c).
*
* ACL support is not implemented.
*/
#include "ubifs.h"
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/xattr.h>
#include <linux/posix_acl_xattr.h>
/*
* Limit the number of extended attributes per inode so that the total size
* (@xattr_size) is guaranteeded to fit in an 'unsigned int'.
*/
#define MAX_XATTRS_PER_INODE 65535
/*
* Extended attribute type constants.
*
* USER_XATTR: user extended attribute ("user.*")
* TRUSTED_XATTR: trusted extended attribute ("trusted.*)
* SECURITY_XATTR: security extended attribute ("security.*")
*/
enum {
USER_XATTR,
TRUSTED_XATTR,
SECURITY_XATTR,
};
static const struct inode_operations empty_iops;
static const struct file_operations empty_fops;
/**
* create_xattr - create an extended attribute.
* @c: UBIFS file-system description object
* @host: host inode
* @nm: extended attribute name
* @value: extended attribute value
* @size: size of extended attribute value
*
* This is a helper function which creates an extended attribute of name @nm
* and value @value for inode @host. The host inode is also updated on flash
* because the ctime and extended attribute accounting data changes. This
* function returns zero in case of success and a negative error code in case
* of failure.
*/
static int create_xattr(struct ubifs_info *c, struct inode *host,
const struct qstr *nm, const void *value, int size)
{
int err;
struct inode *inode;
struct ubifs_inode *ui, *host_ui = ubifs_inode(host);
struct ubifs_budget_req req = { .new_ino = 1, .new_dent = 1,
.new_ino_d = ALIGN(size, 8), .dirtied_ino = 1,
.dirtied_ino_d = ALIGN(host_ui->data_len, 8) };
if (host_ui->xattr_cnt >= MAX_XATTRS_PER_INODE)
return -ENOSPC;
/*
* Linux limits the maximum size of the extended attribute names list
* to %XATTR_LIST_MAX. This means we should not allow creating more
* extended attributes if the name list becomes larger. This limitation
* is artificial for UBIFS, though.
*/
if (host_ui->xattr_names + host_ui->xattr_cnt +
nm->len + 1 > XATTR_LIST_MAX)
return -ENOSPC;
err = ubifs_budget_space(c, &req);
if (err)
return err;
inode = ubifs_new_inode(c, host, S_IFREG | S_IRWXUGO);
if (IS_ERR(inode)) {
err = PTR_ERR(inode);
goto out_budg;
}
/* Re-define all operations to be "nothing" */
inode->i_mapping->a_ops = &empty_aops;
inode->i_op = &empty_iops;
inode->i_fop = &empty_fops;
inode->i_flags |= S_SYNC | S_NOATIME | S_NOCMTIME | S_NOQUOTA;
ui = ubifs_inode(inode);
ui->xattr = 1;
ui->flags |= UBIFS_XATTR_FL;
ui->data = kmalloc(size, GFP_NOFS);
if (!ui->data) {
err = -ENOMEM;
goto out_free;
}
memcpy(ui->data, value, size);
inode->i_size = ui->ui_size = size;
ui->data_len = size;
mutex_lock(&host_ui->ui_mutex);
host->i_ctime = ubifs_current_time(host);
host_ui->xattr_cnt += 1;
host_ui->xattr_size += CALC_DENT_SIZE(nm->len);
host_ui->xattr_size += CALC_XATTR_BYTES(size);
host_ui->xattr_names += nm->len;
err = ubifs_jnl_update(c, host, nm, inode, 0, 1);
if (err)
goto out_cancel;
mutex_unlock(&host_ui->ui_mutex);
ubifs_release_budget(c, &req);
insert_inode_hash(inode);
iput(inode);
return 0;
out_cancel:
host_ui->xattr_cnt -= 1;
host_ui->xattr_size -= CALC_DENT_SIZE(nm->len);
host_ui->xattr_size -= CALC_XATTR_BYTES(size);
mutex_unlock(&host_ui->ui_mutex);
out_free:
make_bad_inode(inode);
iput(inode);
out_budg:
ubifs_release_budget(c, &req);
return err;
}
/**
* change_xattr - change an extended attribute.
* @c: UBIFS file-system description object
* @host: host inode
* @inode: extended attribute inode
* @value: extended attribute value
* @size: size of extended attribute value
*
* This helper function changes the value of extended attribute @inode with new
* data from @value. Returns zero in case of success and a negative error code
* in case of failure.
*/
static int change_xattr(struct ubifs_info *c, struct inode *host,
struct inode *inode, const void *value, int size)
{
int err;
struct ubifs_inode *host_ui = ubifs_inode(host);
struct ubifs_inode *ui = ubifs_inode(inode);
struct ubifs_budget_req req = { .dirtied_ino = 2,
.dirtied_ino_d = ALIGN(size, 8) + ALIGN(host_ui->data_len, 8) };
ubifs_assert(ui->data_len == inode->i_size);
err = ubifs_budget_space(c, &req);
if (err)
return err;
kfree(ui->data);
ui->data = kmalloc(size, GFP_NOFS);
if (!ui->data) {
err = -ENOMEM;
goto out_free;
}
memcpy(ui->data, value, size);
inode->i_size = ui->ui_size = size;
ui->data_len = size;
mutex_lock(&host_ui->ui_mutex);
host->i_ctime = ubifs_current_time(host);
host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len);
host_ui->xattr_size += CALC_XATTR_BYTES(size);
/*
* It is important to write the host inode after the xattr inode
* because if the host inode gets synchronized (via 'fsync()'), then
* the extended attribute inode gets synchronized, because it goes
* before the host inode in the write-buffer.
*/
err = ubifs_jnl_change_xattr(c, inode, host);
if (err)
goto out_cancel;
mutex_unlock(&host_ui->ui_mutex);
ubifs_release_budget(c, &req);
return 0;
out_cancel:
host_ui->xattr_size -= CALC_XATTR_BYTES(size);
host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len);
mutex_unlock(&host_ui->ui_mutex);
make_bad_inode(inode);
out_free:
ubifs_release_budget(c, &req);
return err;
}
/**
* check_namespace - check extended attribute name-space.
* @nm: extended attribute name
*
* This function makes sure the extended attribute name belongs to one of the
* supported extended attribute name-spaces. Returns name-space index in case
* of success and a negative error code in case of failure.
*/
static int check_namespace(const struct qstr *nm)
{
int type;
if (nm->len > UBIFS_MAX_NLEN)
return -ENAMETOOLONG;
if (!strncmp(nm->name, XATTR_TRUSTED_PREFIX,
XATTR_TRUSTED_PREFIX_LEN)) {
if (nm->name[sizeof(XATTR_TRUSTED_PREFIX) - 1] == '\0')
return -EINVAL;
type = TRUSTED_XATTR;
} else if (!strncmp(nm->name, XATTR_USER_PREFIX,
XATTR_USER_PREFIX_LEN)) {
if (nm->name[XATTR_USER_PREFIX_LEN] == '\0')
return -EINVAL;
type = USER_XATTR;
} else if (!strncmp(nm->name, XATTR_SECURITY_PREFIX,
XATTR_SECURITY_PREFIX_LEN)) {
if (nm->name[sizeof(XATTR_SECURITY_PREFIX) - 1] == '\0')
return -EINVAL;
type = SECURITY_XATTR;
} else
return -EOPNOTSUPP;
return type;
}
static struct inode *iget_xattr(struct ubifs_info *c, ino_t inum)
{
struct inode *inode;
inode = ubifs_iget(c->vfs_sb, inum);
if (IS_ERR(inode)) {
ubifs_err("dead extended attribute entry, error %d",
(int)PTR_ERR(inode));
return inode;
}
if (ubifs_inode(inode)->xattr)
return inode;
ubifs_err("corrupt extended attribute entry");
iput(inode);
return ERR_PTR(-EINVAL);
}
int ubifs_setxattr(struct dentry *dentry, const char *name,
const void *value, size_t size, int flags)
{
struct inode *inode, *host = dentry->d_inode;
struct ubifs_info *c = host->i_sb->s_fs_info;
struct qstr nm = { .name = name, .len = strlen(name) };
struct ubifs_dent_node *xent;
union ubifs_key key;
int err, type;
dbg_gen("xattr '%s', host ino %lu ('%.*s'), size %zd", name,
host->i_ino, dentry->d_name.len, dentry->d_name.name, size);
ubifs_assert(mutex_is_locked(&host->i_mutex));
if (size > UBIFS_MAX_INO_DATA)
return -ERANGE;
type = check_namespace(&nm);
if (type < 0)
return type;
xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
if (!xent)
return -ENOMEM;
/*
* The extended attribute entries are stored in LNC, so multiple
* look-ups do not involve reading the flash.
*/
xent_key_init(c, &key, host->i_ino, &nm);
err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
if (err) {
if (err != -ENOENT)
goto out_free;
if (flags & XATTR_REPLACE)
/* We are asked not to create the xattr */
err = -ENODATA;
else
err = create_xattr(c, host, &nm, value, size);
goto out_free;
}
if (flags & XATTR_CREATE) {
/* We are asked not to replace the xattr */
err = -EEXIST;
goto out_free;
}
inode = iget_xattr(c, le64_to_cpu(xent->inum));
if (IS_ERR(inode)) {
err = PTR_ERR(inode);
goto out_free;
}
err = change_xattr(c, host, inode, value, size);
iput(inode);
out_free:
kfree(xent);
return err;
}
ssize_t ubifs_getxattr(struct dentry *dentry, const char *name, void *buf,
size_t size)
{
struct inode *inode, *host = dentry->d_inode;
struct ubifs_info *c = host->i_sb->s_fs_info;
struct qstr nm = { .name = name, .len = strlen(name) };
struct ubifs_inode *ui;
struct ubifs_dent_node *xent;
union ubifs_key key;
int err;
dbg_gen("xattr '%s', ino %lu ('%.*s'), buf size %zd", name,
host->i_ino, dentry->d_name.len, dentry->d_name.name, size);
err = check_namespace(&nm);
if (err < 0)
return err;
xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
if (!xent)
return -ENOMEM;
xent_key_init(c, &key, host->i_ino, &nm);
err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
if (err) {
if (err == -ENOENT)
err = -ENODATA;
goto out_unlock;
}
inode = iget_xattr(c, le64_to_cpu(xent->inum));
if (IS_ERR(inode)) {
err = PTR_ERR(inode);
goto out_unlock;
}
ui = ubifs_inode(inode);
ubifs_assert(inode->i_size == ui->data_len);
ubifs_assert(ubifs_inode(host)->xattr_size > ui->data_len);
if (buf) {
/* If @buf is %NULL we are supposed to return the length */
if (ui->data_len > size) {
dbg_err("buffer size %zd, xattr len %d",
size, ui->data_len);
err = -ERANGE;
goto out_iput;
}
memcpy(buf, ui->data, ui->data_len);
}
err = ui->data_len;
out_iput:
iput(inode);
out_unlock:
kfree(xent);
return err;
}
ssize_t ubifs_listxattr(struct dentry *dentry, char *buffer, size_t size)
{
union ubifs_key key;
struct inode *host = dentry->d_inode;
struct ubifs_info *c = host->i_sb->s_fs_info;
struct ubifs_inode *host_ui = ubifs_inode(host);
struct ubifs_dent_node *xent, *pxent = NULL;
int err, len, written = 0;
struct qstr nm = { .name = NULL };
dbg_gen("ino %lu ('%.*s'), buffer size %zd", host->i_ino,
dentry->d_name.len, dentry->d_name.name, size);
len = host_ui->xattr_names + host_ui->xattr_cnt;
if (!buffer)
/*
* We should return the minimum buffer size which will fit a
* null-terminated list of all the extended attribute names.
*/
return len;
if (len > size)
return -ERANGE;
lowest_xent_key(c, &key, host->i_ino);
while (1) {
int type;
xent = ubifs_tnc_next_ent(c, &key, &nm);
if (IS_ERR(xent)) {
err = PTR_ERR(xent);
break;
}
nm.name = xent->name;
nm.len = le16_to_cpu(xent->nlen);
type = check_namespace(&nm);
if (unlikely(type < 0)) {
err = type;
break;
}
/* Show trusted namespace only for "power" users */
if (type != TRUSTED_XATTR || capable(CAP_SYS_ADMIN)) {
memcpy(buffer + written, nm.name, nm.len + 1);
written += nm.len + 1;
}
kfree(pxent);
pxent = xent;
key_read(c, &xent->key, &key);
}
kfree(pxent);
if (err != -ENOENT) {
ubifs_err("cannot find next direntry, error %d", err);
return err;
}
ubifs_assert(written <= size);
return written;
}
static int remove_xattr(struct ubifs_info *c, struct inode *host,
struct inode *inode, const struct qstr *nm)
{
int err;
struct ubifs_inode *host_ui = ubifs_inode(host);
struct ubifs_inode *ui = ubifs_inode(inode);
struct ubifs_budget_req req = { .dirtied_ino = 2, .mod_dent = 1,
.dirtied_ino_d = ALIGN(host_ui->data_len, 8) };
ubifs_assert(ui->data_len == inode->i_size);
err = ubifs_budget_space(c, &req);
if (err)
return err;
mutex_lock(&host_ui->ui_mutex);
host->i_ctime = ubifs_current_time(host);
host_ui->xattr_cnt -= 1;
host_ui->xattr_size -= CALC_DENT_SIZE(nm->len);
host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len);
host_ui->xattr_names -= nm->len;
err = ubifs_jnl_delete_xattr(c, host, inode, nm);
if (err)
goto out_cancel;
mutex_unlock(&host_ui->ui_mutex);
ubifs_release_budget(c, &req);
return 0;
out_cancel:
host_ui->xattr_cnt += 1;
host_ui->xattr_size += CALC_DENT_SIZE(nm->len);
host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len);
mutex_unlock(&host_ui->ui_mutex);
ubifs_release_budget(c, &req);
make_bad_inode(inode);
return err;
}
int ubifs_removexattr(struct dentry *dentry, const char *name)
{
struct inode *inode, *host = dentry->d_inode;
struct ubifs_info *c = host->i_sb->s_fs_info;
struct qstr nm = { .name = name, .len = strlen(name) };
struct ubifs_dent_node *xent;
union ubifs_key key;
int err;
dbg_gen("xattr '%s', ino %lu ('%.*s')", name,
host->i_ino, dentry->d_name.len, dentry->d_name.name);
ubifs_assert(mutex_is_locked(&host->i_mutex));
err = check_namespace(&nm);
if (err < 0)
return err;
xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
if (!xent)
return -ENOMEM;
xent_key_init(c, &key, host->i_ino, &nm);
err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
if (err) {
if (err == -ENOENT)
err = -ENODATA;
goto out_free;
}
inode = iget_xattr(c, le64_to_cpu(xent->inum));
if (IS_ERR(inode)) {
err = PTR_ERR(inode);
goto out_free;
}
ubifs_assert(inode->i_nlink == 1);
inode->i_nlink = 0;
err = remove_xattr(c, host, inode, &nm);
if (err)
inode->i_nlink = 1;
/* If @i_nlink is 0, 'iput()' will delete the inode */
iput(inode);
out_free:
kfree(xent);
return err;
}