linux/fs/ubifs/xattr.c
Richard Weinberger 11a6fc3dc7 ubifs: xattr: Don't operate on deleted inodes
xattr operations can race with unlink and the following assert triggers:
UBIFS assert failed in ubifs_jnl_change_xattr at 1606 (pid 6256)

Fix this by checking i_nlink before working on the host inode.

Cc: <stable@vger.kernel.org>
Fixes: 1e51764a3c ("UBIFS: add new flash file system")
Signed-off-by: Richard Weinberger <richard@nod.at>
2018-08-15 00:06:15 +02:00

704 lines
18 KiB
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>
/*
* 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 fscrypt_name *nm, const void *value, int size)
{
int err, names_len;
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) {
ubifs_err(c, "inode %lu already has too many xattrs (%d), cannot create more",
host->i_ino, host_ui->xattr_cnt);
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.
*/
names_len = host_ui->xattr_names + host_ui->xattr_cnt + fname_len(nm) + 1;
if (names_len > XATTR_LIST_MAX) {
ubifs_err(c, "cannot add one more xattr name to inode %lu, total names length would become %d, max. is %d",
host->i_ino, names_len, 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;
ui = ubifs_inode(inode);
ui->xattr = 1;
ui->flags |= UBIFS_XATTR_FL;
ui->data = kmemdup(value, size, GFP_NOFS);
if (!ui->data) {
err = -ENOMEM;
goto out_free;
}
inode->i_size = ui->ui_size = size;
ui->data_len = size;
mutex_lock(&host_ui->ui_mutex);
if (!host->i_nlink) {
err = -ENOENT;
goto out_noent;
}
host->i_ctime = current_time(host);
host_ui->xattr_cnt += 1;
host_ui->xattr_size += CALC_DENT_SIZE(fname_len(nm));
host_ui->xattr_size += CALC_XATTR_BYTES(size);
host_ui->xattr_names += fname_len(nm);
/*
* We handle UBIFS_XATTR_NAME_ENCRYPTION_CONTEXT here because we
* have to set the UBIFS_CRYPT_FL flag on the host inode.
* To avoid multiple updates of the same inode in the same operation,
* let's do it here.
*/
if (strcmp(fname_name(nm), UBIFS_XATTR_NAME_ENCRYPTION_CONTEXT) == 0)
host_ui->flags |= UBIFS_CRYPT_FL;
err = ubifs_jnl_update(c, host, nm, inode, 0, 1);
if (err)
goto out_cancel;
ubifs_set_inode_flags(host);
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(fname_len(nm));
host_ui->xattr_size -= CALC_XATTR_BYTES(size);
host_ui->xattr_names -= fname_len(nm);
host_ui->flags &= ~UBIFS_CRYPT_FL;
out_noent:
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);
void *buf = NULL;
int old_size;
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;
buf = kmemdup(value, size, GFP_NOFS);
if (!buf) {
err = -ENOMEM;
goto out_free;
}
mutex_lock(&ui->ui_mutex);
kfree(ui->data);
ui->data = buf;
inode->i_size = ui->ui_size = size;
old_size = ui->data_len;
ui->data_len = size;
mutex_unlock(&ui->ui_mutex);
mutex_lock(&host_ui->ui_mutex);
if (!host->i_nlink) {
err = -ENOENT;
goto out_noent;
}
host->i_ctime = current_time(host);
host_ui->xattr_size -= CALC_XATTR_BYTES(old_size);
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(old_size);
out_noent:
mutex_unlock(&host_ui->ui_mutex);
make_bad_inode(inode);
out_free:
ubifs_release_budget(c, &req);
return err;
}
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(c, "dead extended attribute entry, error %d",
(int)PTR_ERR(inode));
return inode;
}
if (ubifs_inode(inode)->xattr)
return inode;
ubifs_err(c, "corrupt extended attribute entry");
iput(inode);
return ERR_PTR(-EINVAL);
}
int ubifs_xattr_set(struct inode *host, const char *name, const void *value,
size_t size, int flags, bool check_lock)
{
struct inode *inode;
struct ubifs_info *c = host->i_sb->s_fs_info;
struct fscrypt_name nm = { .disk_name = FSTR_INIT((char *)name, strlen(name))};
struct ubifs_dent_node *xent;
union ubifs_key key;
int err;
if (check_lock)
ubifs_assert(inode_is_locked(host));
if (size > UBIFS_MAX_INO_DATA)
return -ERANGE;
if (fname_len(&nm) > UBIFS_MAX_NLEN)
return -ENAMETOOLONG;
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_xattr_get(struct inode *host, const char *name, void *buf,
size_t size)
{
struct inode *inode;
struct ubifs_info *c = host->i_sb->s_fs_info;
struct fscrypt_name nm = { .disk_name = FSTR_INIT((char *)name, strlen(name))};
struct ubifs_inode *ui;
struct ubifs_dent_node *xent;
union ubifs_key key;
int err;
if (fname_len(&nm) > UBIFS_MAX_NLEN)
return -ENAMETOOLONG;
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);
mutex_lock(&ui->ui_mutex);
if (buf) {
/* If @buf is %NULL we are supposed to return the length */
if (ui->data_len > size) {
err = -ERANGE;
goto out_iput;
}
memcpy(buf, ui->data, ui->data_len);
}
err = ui->data_len;
out_iput:
mutex_unlock(&ui->ui_mutex);
iput(inode);
out_unlock:
kfree(xent);
return err;
}
static bool xattr_visible(const char *name)
{
/* File encryption related xattrs are for internal use only */
if (strcmp(name, UBIFS_XATTR_NAME_ENCRYPTION_CONTEXT) == 0)
return false;
/* Show trusted namespace only for "power" users */
if (strncmp(name, XATTR_TRUSTED_PREFIX,
XATTR_TRUSTED_PREFIX_LEN) == 0 && !capable(CAP_SYS_ADMIN))
return false;
return true;
}
ssize_t ubifs_listxattr(struct dentry *dentry, char *buffer, size_t size)
{
union ubifs_key key;
struct inode *host = d_inode(dentry);
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 fscrypt_name nm = {0};
dbg_gen("ino %lu ('%pd'), buffer size %zd", host->i_ino,
dentry, 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) {
xent = ubifs_tnc_next_ent(c, &key, &nm);
if (IS_ERR(xent)) {
err = PTR_ERR(xent);
break;
}
fname_name(&nm) = xent->name;
fname_len(&nm) = le16_to_cpu(xent->nlen);
if (xattr_visible(xent->name)) {
memcpy(buffer + written, fname_name(&nm), fname_len(&nm) + 1);
written += fname_len(&nm) + 1;
}
kfree(pxent);
pxent = xent;
key_read(c, &xent->key, &key);
}
kfree(pxent);
if (err != -ENOENT) {
ubifs_err(c, "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 fscrypt_name *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);
if (!host->i_nlink) {
err = -ENOENT;
goto out_noent;
}
host->i_ctime = current_time(host);
host_ui->xattr_cnt -= 1;
host_ui->xattr_size -= CALC_DENT_SIZE(fname_len(nm));
host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len);
host_ui->xattr_names -= fname_len(nm);
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(fname_len(nm));
host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len);
host_ui->xattr_names += fname_len(nm);
out_noent:
mutex_unlock(&host_ui->ui_mutex);
ubifs_release_budget(c, &req);
make_bad_inode(inode);
return err;
}
/**
* ubifs_evict_xattr_inode - Evict an xattr inode.
* @c: UBIFS file-system description object
* @xattr_inum: xattr inode number
*
* When an inode that hosts xattrs is being removed we have to make sure
* that cached inodes of the xattrs also get removed from the inode cache
* otherwise we'd waste memory. This function looks up an inode from the
* inode cache and clears the link counter such that iput() will evict
* the inode.
*/
void ubifs_evict_xattr_inode(struct ubifs_info *c, ino_t xattr_inum)
{
struct inode *inode;
inode = ilookup(c->vfs_sb, xattr_inum);
if (inode) {
clear_nlink(inode);
iput(inode);
}
}
static int ubifs_xattr_remove(struct inode *host, const char *name)
{
struct inode *inode;
struct ubifs_info *c = host->i_sb->s_fs_info;
struct fscrypt_name nm = { .disk_name = FSTR_INIT((char *)name, strlen(name))};
struct ubifs_dent_node *xent;
union ubifs_key key;
int err;
ubifs_assert(inode_is_locked(host));
if (!host->i_nlink)
return -ENOENT;
if (fname_len(&nm) > UBIFS_MAX_NLEN)
return -ENAMETOOLONG;
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);
clear_nlink(inode);
err = remove_xattr(c, host, inode, &nm);
if (err)
set_nlink(inode, 1);
/* If @i_nlink is 0, 'iput()' will delete the inode */
iput(inode);
out_free:
kfree(xent);
return err;
}
#ifdef CONFIG_UBIFS_FS_SECURITY
static int init_xattrs(struct inode *inode, const struct xattr *xattr_array,
void *fs_info)
{
const struct xattr *xattr;
char *name;
int err = 0;
for (xattr = xattr_array; xattr->name != NULL; xattr++) {
name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
strlen(xattr->name) + 1, GFP_NOFS);
if (!name) {
err = -ENOMEM;
break;
}
strcpy(name, XATTR_SECURITY_PREFIX);
strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
/*
* creating a new inode without holding the inode rwsem,
* no need to check whether inode is locked.
*/
err = ubifs_xattr_set(inode, name, xattr->value,
xattr->value_len, 0, false);
kfree(name);
if (err < 0)
break;
}
return err;
}
int ubifs_init_security(struct inode *dentry, struct inode *inode,
const struct qstr *qstr)
{
int err;
err = security_inode_init_security(inode, dentry, qstr,
&init_xattrs, 0);
if (err) {
struct ubifs_info *c = dentry->i_sb->s_fs_info;
ubifs_err(c, "cannot initialize security for inode %lu, error %d",
inode->i_ino, err);
}
return err;
}
#endif
static int xattr_get(const struct xattr_handler *handler,
struct dentry *dentry, struct inode *inode,
const char *name, void *buffer, size_t size)
{
dbg_gen("xattr '%s', ino %lu ('%pd'), buf size %zd", name,
inode->i_ino, dentry, size);
name = xattr_full_name(handler, name);
return ubifs_xattr_get(inode, name, buffer, size);
}
static int xattr_set(const struct xattr_handler *handler,
struct dentry *dentry, struct inode *inode,
const char *name, const void *value,
size_t size, int flags)
{
dbg_gen("xattr '%s', host ino %lu ('%pd'), size %zd",
name, inode->i_ino, dentry, size);
name = xattr_full_name(handler, name);
if (value)
return ubifs_xattr_set(inode, name, value, size, flags, true);
else
return ubifs_xattr_remove(inode, name);
}
static const struct xattr_handler ubifs_user_xattr_handler = {
.prefix = XATTR_USER_PREFIX,
.get = xattr_get,
.set = xattr_set,
};
static const struct xattr_handler ubifs_trusted_xattr_handler = {
.prefix = XATTR_TRUSTED_PREFIX,
.get = xattr_get,
.set = xattr_set,
};
#ifdef CONFIG_UBIFS_FS_SECURITY
static const struct xattr_handler ubifs_security_xattr_handler = {
.prefix = XATTR_SECURITY_PREFIX,
.get = xattr_get,
.set = xattr_set,
};
#endif
const struct xattr_handler *ubifs_xattr_handlers[] = {
&ubifs_user_xattr_handler,
&ubifs_trusted_xattr_handler,
#ifdef CONFIG_UBIFS_FS_SECURITY
&ubifs_security_xattr_handler,
#endif
NULL
};