/*
   * 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 = 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);
  	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 = 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);
  	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 = QSTR_INIT(name, strlen(name));
  	struct ubifs_dent_node *xent;
  	union ubifs_key key;
  	int err, type;
  
  	dbg_gen("xattr '%s', host ino %lu ('%pd'), size %zd", name,
  		host->i_ino, dentry, 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 = QSTR_INIT(name, strlen(name));
  	struct ubifs_inode *ui;
  	struct ubifs_dent_node *xent;
  	union ubifs_key key;
  	int err;
  
  	dbg_gen("xattr '%s', ino %lu ('%pd'), buf size %zd", name,
  		host->i_ino, dentry, 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) {
  			ubifs_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 ('%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) {
  		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 = QSTR_INIT(name, strlen(name));
  	struct ubifs_dent_node *xent;
  	union ubifs_key key;
  	int err;
  
  	dbg_gen("xattr '%s', ino %lu ('%pd')", name,
  		host->i_ino, dentry);
  	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);
  	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;
  }