/*

   * Copyright (C) 2002,2003 by Andreas Gruenbacher <a.gruenbacher@computer.org>

   *

   * Fixes from William Schumacher incorporated on 15 March 2001.
   *    (Reported by Charles Bertsch, <CBertsch@microtest.com>).

   */
  
  /*
   *  This file contains generic functions for manipulating
   *  POSIX 1003.1e draft standard 17 ACLs.
   */
  
  #include <linux/kernel.h>
  #include <linux/slab.h>

  #include <linux/atomic.h>

  #include <linux/fs.h>
  #include <linux/sched.h>

  #include <linux/cred.h>

  #include <linux/posix_acl.h>

  #include <linux/posix_acl_xattr.h>

  #include <linux/xattr.h>

  #include <linux/export.h>

  #include <linux/user_namespace.h>

  static struct posix_acl **acl_by_type(struct inode *inode, int type)

  {
  	switch (type) {
  	case ACL_TYPE_ACCESS:
  		return &inode->i_acl;
  	case ACL_TYPE_DEFAULT:
  		return &inode->i_default_acl;
  	default:
  		BUG();
  	}
  }

  
  struct posix_acl *get_cached_acl(struct inode *inode, int type)
  {
  	struct posix_acl **p = acl_by_type(inode, type);

  	struct posix_acl *acl;
  
  	for (;;) {
  		rcu_read_lock();
  		acl = rcu_dereference(*p);
  		if (!acl || is_uncached_acl(acl) ||
  		    atomic_inc_not_zero(&acl->a_refcount))
  			break;
  		rcu_read_unlock();
  		cpu_relax();

  	}

  	rcu_read_unlock();

  	return acl;
  }
  EXPORT_SYMBOL(get_cached_acl);
  
  struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type)
  {
  	return rcu_dereference(*acl_by_type(inode, type));
  }
  EXPORT_SYMBOL(get_cached_acl_rcu);
  
  void set_cached_acl(struct inode *inode, int type, struct posix_acl *acl)
  {
  	struct posix_acl **p = acl_by_type(inode, type);
  	struct posix_acl *old;

  
  	old = xchg(p, posix_acl_dup(acl));
  	if (!is_uncached_acl(old))

  		posix_acl_release(old);
  }
  EXPORT_SYMBOL(set_cached_acl);

  static void __forget_cached_acl(struct posix_acl **p)

  {

  	struct posix_acl *old;

  
  	old = xchg(p, ACL_NOT_CACHED);
  	if (!is_uncached_acl(old))

  		posix_acl_release(old);
  }

  
  void forget_cached_acl(struct inode *inode, int type)
  {
  	__forget_cached_acl(acl_by_type(inode, type));
  }

  EXPORT_SYMBOL(forget_cached_acl);
  
  void forget_all_cached_acls(struct inode *inode)
  {

  	__forget_cached_acl(&inode->i_acl);
  	__forget_cached_acl(&inode->i_default_acl);

  }
  EXPORT_SYMBOL(forget_all_cached_acls);

  struct posix_acl *get_acl(struct inode *inode, int type)
  {

  	void *sentinel;
  	struct posix_acl **p;

  	struct posix_acl *acl;

  	/*
  	 * The sentinel is used to detect when another operation like
  	 * set_cached_acl() or forget_cached_acl() races with get_acl().
  	 * It is guaranteed that is_uncached_acl(sentinel) is true.
  	 */

  	acl = get_cached_acl(inode, type);

  	if (!is_uncached_acl(acl))

  		return acl;
  
  	if (!IS_POSIXACL(inode))
  		return NULL;

  	sentinel = uncached_acl_sentinel(current);
  	p = acl_by_type(inode, type);
  
  	/*
  	 * If the ACL isn't being read yet, set our sentinel.  Otherwise, the
  	 * current value of the ACL will not be ACL_NOT_CACHED and so our own
  	 * sentinel will not be set; another task will update the cache.  We
  	 * could wait for that other task to complete its job, but it's easier
  	 * to just call ->get_acl to fetch the ACL ourself.  (This is going to
  	 * be an unlikely race.)
  	 */
  	if (cmpxchg(p, ACL_NOT_CACHED, sentinel) != ACL_NOT_CACHED)
  		/* fall through */ ;

  	/*

  	 * Normally, the ACL returned by ->get_acl will be cached.
  	 * A filesystem can prevent that by calling
  	 * forget_cached_acl(inode, type) in ->get_acl.

  	 *
  	 * If the filesystem doesn't have a get_acl() function at all, we'll
  	 * just create the negative cache entry.
  	 */
  	if (!inode->i_op->get_acl) {
  		set_cached_acl(inode, type, NULL);
  		return NULL;
  	}

  	acl = inode->i_op->get_acl(inode, type);
  
  	if (IS_ERR(acl)) {
  		/*
  		 * Remove our sentinel so that we don't block future attempts
  		 * to cache the ACL.
  		 */
  		cmpxchg(p, sentinel, ACL_NOT_CACHED);
  		return acl;
  	}
  
  	/*
  	 * Cache the result, but only if our sentinel is still in place.
  	 */
  	posix_acl_dup(acl);
  	if (unlikely(cmpxchg(p, sentinel, acl) != sentinel))
  		posix_acl_release(acl);
  	return acl;

  }
  EXPORT_SYMBOL(get_acl);

  /*

   * Init a fresh posix_acl
   */
  void
  posix_acl_init(struct posix_acl *acl, int count)
  {
  	atomic_set(&acl->a_refcount, 1);
  	acl->a_count = count;
  }

  EXPORT_SYMBOL(posix_acl_init);

  
  /*

   * Allocate a new ACL with the specified number of entries.
   */
  struct posix_acl *

  posix_acl_alloc(int count, gfp_t flags)

  {
  	const size_t size = sizeof(struct posix_acl) +
  	                    count * sizeof(struct posix_acl_entry);
  	struct posix_acl *acl = kmalloc(size, flags);

  	if (acl)
  		posix_acl_init(acl, count);

  	return acl;
  }

  EXPORT_SYMBOL(posix_acl_alloc);

  
  /*
   * Clone an ACL.
   */

  static struct posix_acl *

  posix_acl_clone(const struct posix_acl *acl, gfp_t flags)

  {
  	struct posix_acl *clone = NULL;
  
  	if (acl) {
  		int size = sizeof(struct posix_acl) + acl->a_count *
  		           sizeof(struct posix_acl_entry);

  		clone = kmemdup(acl, size, flags);
  		if (clone)

  			atomic_set(&clone->a_refcount, 1);

  	}
  	return clone;
  }
  
  /*
   * Check if an acl is valid. Returns 0 if it is, or -E... otherwise.
   */
  int

  posix_acl_valid(struct user_namespace *user_ns, const struct posix_acl *acl)

  {
  	const struct posix_acl_entry *pa, *pe;
  	int state = ACL_USER_OBJ;

  	int needs_mask = 0;
  
  	FOREACH_ACL_ENTRY(pa, acl, pe) {
  		if (pa->e_perm & ~(ACL_READ|ACL_WRITE|ACL_EXECUTE))
  			return -EINVAL;
  		switch (pa->e_tag) {
  			case ACL_USER_OBJ:
  				if (state == ACL_USER_OBJ) {

  					state = ACL_USER;
  					break;
  				}
  				return -EINVAL;
  
  			case ACL_USER:
  				if (state != ACL_USER)
  					return -EINVAL;

  				if (!kuid_has_mapping(user_ns, pa->e_uid))

  					return -EINVAL;

  				needs_mask = 1;
  				break;
  
  			case ACL_GROUP_OBJ:
  				if (state == ACL_USER) {

  					state = ACL_GROUP;
  					break;
  				}
  				return -EINVAL;
  
  			case ACL_GROUP:
  				if (state != ACL_GROUP)
  					return -EINVAL;

  				if (!kgid_has_mapping(user_ns, pa->e_gid))

  					return -EINVAL;

  				needs_mask = 1;
  				break;
  
  			case ACL_MASK:
  				if (state != ACL_GROUP)
  					return -EINVAL;
  				state = ACL_OTHER;
  				break;
  
  			case ACL_OTHER:
  				if (state == ACL_OTHER ||
  				    (state == ACL_GROUP && !needs_mask)) {
  					state = 0;
  					break;
  				}
  				return -EINVAL;
  
  			default:
  				return -EINVAL;
  		}
  	}
  	if (state == 0)
  		return 0;
  	return -EINVAL;
  }

  EXPORT_SYMBOL(posix_acl_valid);

  
  /*
   * Returns 0 if the acl can be exactly represented in the traditional
   * file mode permission bits, or else 1. Returns -E... on error.
   */
  int

  posix_acl_equiv_mode(const struct posix_acl *acl, umode_t *mode_p)

  {
  	const struct posix_acl_entry *pa, *pe;

  	umode_t mode = 0;

  	int not_equiv = 0;

  	/*
  	 * A null ACL can always be presented as mode bits.
  	 */
  	if (!acl)
  		return 0;

  	FOREACH_ACL_ENTRY(pa, acl, pe) {
  		switch (pa->e_tag) {
  			case ACL_USER_OBJ:
  				mode |= (pa->e_perm & S_IRWXO) << 6;
  				break;
  			case ACL_GROUP_OBJ:
  				mode |= (pa->e_perm & S_IRWXO) << 3;
  				break;
  			case ACL_OTHER:
  				mode |= pa->e_perm & S_IRWXO;
  				break;
  			case ACL_MASK:
  				mode = (mode & ~S_IRWXG) |
  				       ((pa->e_perm & S_IRWXO) << 3);
  				not_equiv = 1;
  				break;
  			case ACL_USER:
  			case ACL_GROUP:
  				not_equiv = 1;
  				break;
  			default:
  				return -EINVAL;
  		}
  	}
          if (mode_p)
                  *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
          return not_equiv;
  }

  EXPORT_SYMBOL(posix_acl_equiv_mode);

  
  /*
   * Create an ACL representing the file mode permission bits of an inode.
   */
  struct posix_acl *

  posix_acl_from_mode(umode_t mode, gfp_t flags)

  {
  	struct posix_acl *acl = posix_acl_alloc(3, flags);
  	if (!acl)
  		return ERR_PTR(-ENOMEM);
  
  	acl->a_entries[0].e_tag  = ACL_USER_OBJ;

  	acl->a_entries[0].e_perm = (mode & S_IRWXU) >> 6;
  
  	acl->a_entries[1].e_tag  = ACL_GROUP_OBJ;

  	acl->a_entries[1].e_perm = (mode & S_IRWXG) >> 3;
  
  	acl->a_entries[2].e_tag  = ACL_OTHER;

  	acl->a_entries[2].e_perm = (mode & S_IRWXO);
  	return acl;
  }

  EXPORT_SYMBOL(posix_acl_from_mode);

  
  /*
   * Return 0 if current is granted want access to the inode
   * by the acl. Returns -E... otherwise.
   */
  int
  posix_acl_permission(struct inode *inode, const struct posix_acl *acl, int want)
  {
  	const struct posix_acl_entry *pa, *pe, *mask_obj;
  	int found = 0;

  	want &= MAY_READ | MAY_WRITE | MAY_EXEC | MAY_NOT_BLOCK;

  	FOREACH_ACL_ENTRY(pa, acl, pe) {
                  switch(pa->e_tag) {
                          case ACL_USER_OBJ:
  				/* (May have been checked already) */

  				if (uid_eq(inode->i_uid, current_fsuid()))

                                          goto check_perm;
                                  break;
                          case ACL_USER:

  				if (uid_eq(pa->e_uid, current_fsuid()))

                                          goto mask;
  				break;
                          case ACL_GROUP_OBJ:
                                  if (in_group_p(inode->i_gid)) {
  					found = 1;
  					if ((pa->e_perm & want) == want)
  						goto mask;
                                  }
  				break;
                          case ACL_GROUP:

  				if (in_group_p(pa->e_gid)) {

  					found = 1;
  					if ((pa->e_perm & want) == want)
  						goto mask;
                                  }
                                  break;
                          case ACL_MASK:
                                  break;
                          case ACL_OTHER:
  				if (found)
  					return -EACCES;
  				else
  					goto check_perm;
  			default:
  				return -EIO;
                  }
          }
  	return -EIO;
  
  mask:
  	for (mask_obj = pa+1; mask_obj != pe; mask_obj++) {
  		if (mask_obj->e_tag == ACL_MASK) {
  			if ((pa->e_perm & mask_obj->e_perm & want) == want)
  				return 0;
  			return -EACCES;
  		}
  	}
  
  check_perm:
  	if ((pa->e_perm & want) == want)
  		return 0;
  	return -EACCES;
  }
  
  /*
   * Modify acl when creating a new inode. The caller must ensure the acl is
   * only referenced once.
   *
   * mode_p initially must contain the mode parameter to the open() / creat()
   * system calls. All permissions that are not granted by the acl are removed.
   * The permissions in the acl are changed to reflect the mode_p parameter.
   */

  static int posix_acl_create_masq(struct posix_acl *acl, umode_t *mode_p)

  {
  	struct posix_acl_entry *pa, *pe;
  	struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;

  	umode_t mode = *mode_p;

  	int not_equiv = 0;
  
  	/* assert(atomic_read(acl->a_refcount) == 1); */
  
  	FOREACH_ACL_ENTRY(pa, acl, pe) {
                  switch(pa->e_tag) {
                          case ACL_USER_OBJ:
  				pa->e_perm &= (mode >> 6) | ~S_IRWXO;
  				mode &= (pa->e_perm << 6) | ~S_IRWXU;
  				break;
  
  			case ACL_USER:
  			case ACL_GROUP:
  				not_equiv = 1;
  				break;
  
                          case ACL_GROUP_OBJ:
  				group_obj = pa;
                                  break;
  
                          case ACL_OTHER:
  				pa->e_perm &= mode | ~S_IRWXO;
  				mode &= pa->e_perm | ~S_IRWXO;
                                  break;
  
                          case ACL_MASK:
  				mask_obj = pa;
  				not_equiv = 1;
                                  break;
  
  			default:
  				return -EIO;
                  }
          }
  
  	if (mask_obj) {
  		mask_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
  		mode &= (mask_obj->e_perm << 3) | ~S_IRWXG;
  	} else {
  		if (!group_obj)
  			return -EIO;
  		group_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
  		mode &= (group_obj->e_perm << 3) | ~S_IRWXG;
  	}
  
  	*mode_p = (*mode_p & ~S_IRWXUGO) | mode;
          return not_equiv;
  }
  
  /*
   * Modify the ACL for the chmod syscall.
   */

  static int __posix_acl_chmod_masq(struct posix_acl *acl, umode_t mode)

  {
  	struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
  	struct posix_acl_entry *pa, *pe;
  
  	/* assert(atomic_read(acl->a_refcount) == 1); */
  
  	FOREACH_ACL_ENTRY(pa, acl, pe) {
  		switch(pa->e_tag) {
  			case ACL_USER_OBJ:
  				pa->e_perm = (mode & S_IRWXU) >> 6;
  				break;
  
  			case ACL_USER:
  			case ACL_GROUP:
  				break;
  
  			case ACL_GROUP_OBJ:
  				group_obj = pa;
  				break;
  
  			case ACL_MASK:
  				mask_obj = pa;
  				break;
  
  			case ACL_OTHER:
  				pa->e_perm = (mode & S_IRWXO);
  				break;
  
  			default:
  				return -EIO;
  		}
  	}
  
  	if (mask_obj) {
  		mask_obj->e_perm = (mode & S_IRWXG) >> 3;
  	} else {
  		if (!group_obj)
  			return -EIO;
  		group_obj->e_perm = (mode & S_IRWXG) >> 3;
  	}
  
  	return 0;
  }

  
  int

  __posix_acl_create(struct posix_acl **acl, gfp_t gfp, umode_t *mode_p)

  {
  	struct posix_acl *clone = posix_acl_clone(*acl, gfp);
  	int err = -ENOMEM;
  	if (clone) {
  		err = posix_acl_create_masq(clone, mode_p);
  		if (err < 0) {
  			posix_acl_release(clone);
  			clone = NULL;
  		}
  	}
  	posix_acl_release(*acl);
  	*acl = clone;
  	return err;
  }

  EXPORT_SYMBOL(__posix_acl_create);

  
  int

  __posix_acl_chmod(struct posix_acl **acl, gfp_t gfp, umode_t mode)

  {
  	struct posix_acl *clone = posix_acl_clone(*acl, gfp);
  	int err = -ENOMEM;
  	if (clone) {

  		err = __posix_acl_chmod_masq(clone, mode);

  		if (err) {
  			posix_acl_release(clone);
  			clone = NULL;
  		}
  	}
  	posix_acl_release(*acl);
  	*acl = clone;
  	return err;
  }

  EXPORT_SYMBOL(__posix_acl_chmod);
  
  int

  posix_acl_chmod(struct inode *inode, umode_t mode)

  {
  	struct posix_acl *acl;
  	int ret = 0;
  
  	if (!IS_POSIXACL(inode))
  		return 0;
  	if (!inode->i_op->set_acl)
  		return -EOPNOTSUPP;
  
  	acl = get_acl(inode, ACL_TYPE_ACCESS);

  	if (IS_ERR_OR_NULL(acl)) {
  		if (acl == ERR_PTR(-EOPNOTSUPP))
  			return 0;

  		return PTR_ERR(acl);

  	}

  	ret = __posix_acl_chmod(&acl, GFP_KERNEL, mode);

  	if (ret)
  		return ret;
  	ret = inode->i_op->set_acl(inode, acl, ACL_TYPE_ACCESS);
  	posix_acl_release(acl);
  	return ret;
  }

  EXPORT_SYMBOL(posix_acl_chmod);

  int
  posix_acl_create(struct inode *dir, umode_t *mode,
  		struct posix_acl **default_acl, struct posix_acl **acl)
  {
  	struct posix_acl *p;

  	struct posix_acl *clone;

  	int ret;

  	*acl = NULL;
  	*default_acl = NULL;

  	if (S_ISLNK(*mode) || !IS_POSIXACL(dir))

  		return 0;

  
  	p = get_acl(dir, ACL_TYPE_DEFAULT);

  	if (!p || p == ERR_PTR(-EOPNOTSUPP)) {
  		*mode &= ~current_umask();
  		return 0;

  	}

  	if (IS_ERR(p))
  		return PTR_ERR(p);

  	ret = -ENOMEM;

  	clone = posix_acl_clone(p, GFP_NOFS);
  	if (!clone)

  		goto err_release;

  	ret = posix_acl_create_masq(clone, mode);

  	if (ret < 0)

  		goto err_release_clone;

  	if (ret == 0)
  		posix_acl_release(clone);
  	else
  		*acl = clone;

  	if (!S_ISDIR(*mode))

  		posix_acl_release(p);

  	else

  		*default_acl = p;

  	return 0;

  err_release_clone:

  	posix_acl_release(clone);

  err_release:

  	posix_acl_release(p);

  	return ret;

  }
  EXPORT_SYMBOL_GPL(posix_acl_create);

  /**
   * posix_acl_update_mode  -  update mode in set_acl
   *
   * Update the file mode when setting an ACL: compute the new file permission
   * bits based on the ACL.  In addition, if the ACL is equivalent to the new
   * file mode, set *acl to NULL to indicate that no ACL should be set.
   *
   * As with chmod, clear the setgit bit if the caller is not in the owning group
   * or capable of CAP_FSETID (see inode_change_ok).
   *
   * Called from set_acl inode operations.
   */
  int posix_acl_update_mode(struct inode *inode, umode_t *mode_p,
  			  struct posix_acl **acl)
  {
  	umode_t mode = inode->i_mode;
  	int error;
  
  	error = posix_acl_equiv_mode(*acl, &mode);
  	if (error < 0)
  		return error;
  	if (error == 0)
  		*acl = NULL;
  	if (!in_group_p(inode->i_gid) &&
  	    !capable_wrt_inode_uidgid(inode, CAP_FSETID))
  		mode &= ~S_ISGID;
  	*mode_p = mode;
  	return 0;
  }
  EXPORT_SYMBOL(posix_acl_update_mode);

  /*
   * Fix up the uids and gids in posix acl extended attributes in place.
   */
  static void posix_acl_fix_xattr_userns(
  	struct user_namespace *to, struct user_namespace *from,
  	void *value, size_t size)
  {

  	struct posix_acl_xattr_header *header = value;
  	struct posix_acl_xattr_entry *entry = (void *)(header + 1), *end;

  	int count;
  	kuid_t uid;
  	kgid_t gid;
  
  	if (!value)
  		return;

  	if (size < sizeof(struct posix_acl_xattr_header))

  		return;
  	if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
  		return;
  
  	count = posix_acl_xattr_count(size);
  	if (count < 0)
  		return;
  	if (count == 0)
  		return;
  
  	for (end = entry + count; entry != end; entry++) {
  		switch(le16_to_cpu(entry->e_tag)) {
  		case ACL_USER:
  			uid = make_kuid(from, le32_to_cpu(entry->e_id));
  			entry->e_id = cpu_to_le32(from_kuid(to, uid));
  			break;
  		case ACL_GROUP:
  			gid = make_kgid(from, le32_to_cpu(entry->e_id));
  			entry->e_id = cpu_to_le32(from_kgid(to, gid));
  			break;
  		default:
  			break;
  		}
  	}
  }
  
  void posix_acl_fix_xattr_from_user(void *value, size_t size)
  {
  	struct user_namespace *user_ns = current_user_ns();
  	if (user_ns == &init_user_ns)
  		return;
  	posix_acl_fix_xattr_userns(&init_user_ns, user_ns, value, size);
  }
  
  void posix_acl_fix_xattr_to_user(void *value, size_t size)
  {
  	struct user_namespace *user_ns = current_user_ns();
  	if (user_ns == &init_user_ns)
  		return;
  	posix_acl_fix_xattr_userns(user_ns, &init_user_ns, value, size);
  }
  
  /*
   * Convert from extended attribute to in-memory representation.
   */
  struct posix_acl *
  posix_acl_from_xattr(struct user_namespace *user_ns,
  		     const void *value, size_t size)
  {

  	const struct posix_acl_xattr_header *header = value;
  	const struct posix_acl_xattr_entry *entry = (const void *)(header + 1), *end;

  	int count;
  	struct posix_acl *acl;
  	struct posix_acl_entry *acl_e;
  
  	if (!value)
  		return NULL;

  	if (size < sizeof(struct posix_acl_xattr_header))

  		 return ERR_PTR(-EINVAL);
  	if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
  		return ERR_PTR(-EOPNOTSUPP);
  
  	count = posix_acl_xattr_count(size);
  	if (count < 0)
  		return ERR_PTR(-EINVAL);
  	if (count == 0)
  		return NULL;
  	
  	acl = posix_acl_alloc(count, GFP_NOFS);
  	if (!acl)
  		return ERR_PTR(-ENOMEM);
  	acl_e = acl->a_entries;
  	
  	for (end = entry + count; entry != end; acl_e++, entry++) {
  		acl_e->e_tag  = le16_to_cpu(entry->e_tag);
  		acl_e->e_perm = le16_to_cpu(entry->e_perm);
  
  		switch(acl_e->e_tag) {
  			case ACL_USER_OBJ:
  			case ACL_GROUP_OBJ:
  			case ACL_MASK:
  			case ACL_OTHER:
  				break;
  
  			case ACL_USER:
  				acl_e->e_uid =
  					make_kuid(user_ns,
  						  le32_to_cpu(entry->e_id));
  				if (!uid_valid(acl_e->e_uid))
  					goto fail;
  				break;
  			case ACL_GROUP:
  				acl_e->e_gid =
  					make_kgid(user_ns,
  						  le32_to_cpu(entry->e_id));
  				if (!gid_valid(acl_e->e_gid))
  					goto fail;
  				break;
  
  			default:
  				goto fail;
  		}
  	}
  	return acl;
  
  fail:
  	posix_acl_release(acl);
  	return ERR_PTR(-EINVAL);
  }
  EXPORT_SYMBOL (posix_acl_from_xattr);
  
  /*
   * Convert from in-memory to extended attribute representation.
   */
  int
  posix_acl_to_xattr(struct user_namespace *user_ns, const struct posix_acl *acl,
  		   void *buffer, size_t size)
  {

  	struct posix_acl_xattr_header *ext_acl = buffer;
  	struct posix_acl_xattr_entry *ext_entry;

  	int real_size, n;
  
  	real_size = posix_acl_xattr_size(acl->a_count);
  	if (!buffer)
  		return real_size;
  	if (real_size > size)
  		return -ERANGE;

  	ext_entry = (void *)(ext_acl + 1);

  	ext_acl->a_version = cpu_to_le32(POSIX_ACL_XATTR_VERSION);
  
  	for (n=0; n < acl->a_count; n++, ext_entry++) {
  		const struct posix_acl_entry *acl_e = &acl->a_entries[n];
  		ext_entry->e_tag  = cpu_to_le16(acl_e->e_tag);
  		ext_entry->e_perm = cpu_to_le16(acl_e->e_perm);
  		switch(acl_e->e_tag) {
  		case ACL_USER:
  			ext_entry->e_id =
  				cpu_to_le32(from_kuid(user_ns, acl_e->e_uid));
  			break;
  		case ACL_GROUP:
  			ext_entry->e_id =
  				cpu_to_le32(from_kgid(user_ns, acl_e->e_gid));
  			break;
  		default:
  			ext_entry->e_id = cpu_to_le32(ACL_UNDEFINED_ID);
  			break;
  		}
  	}
  	return real_size;
  }
  EXPORT_SYMBOL (posix_acl_to_xattr);

  
  static int

  posix_acl_xattr_get(const struct xattr_handler *handler,

  		    struct dentry *unused, struct inode *inode,
  		    const char *name, void *value, size_t size)

  {
  	struct posix_acl *acl;
  	int error;

  	if (!IS_POSIXACL(inode))

  		return -EOPNOTSUPP;

  	if (S_ISLNK(inode->i_mode))

  		return -EOPNOTSUPP;

  	acl = get_acl(inode, handler->flags);

  	if (IS_ERR(acl))
  		return PTR_ERR(acl);
  	if (acl == NULL)
  		return -ENODATA;
  
  	error = posix_acl_to_xattr(&init_user_ns, acl, value, size);
  	posix_acl_release(acl);
  
  	return error;
  }

  int
  set_posix_acl(struct inode *inode, int type, struct posix_acl *acl)

  {

  	if (!IS_POSIXACL(inode))
  		return -EOPNOTSUPP;
  	if (!inode->i_op->set_acl)
  		return -EOPNOTSUPP;

  	if (type == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode))
  		return acl ? -EACCES : 0;

  	if (!inode_owner_or_capable(inode))
  		return -EPERM;

  	if (acl) {

  		int ret = posix_acl_valid(inode->i_sb->s_user_ns, acl);

  		if (ret)
  			return ret;
  	}
  	return inode->i_op->set_acl(inode, acl, type);
  }
  EXPORT_SYMBOL(set_posix_acl);
  
  static int
  posix_acl_xattr_set(const struct xattr_handler *handler,
  		    struct dentry *unused, struct inode *inode,
  		    const char *name, const void *value,
  		    size_t size, int flags)
  {
  	struct posix_acl *acl = NULL;
  	int ret;

  	if (value) {
  		acl = posix_acl_from_xattr(&init_user_ns, value, size);
  		if (IS_ERR(acl))
  			return PTR_ERR(acl);

  	}

  	ret = set_posix_acl(inode, handler->flags, acl);

  	posix_acl_release(acl);
  	return ret;
  }

  static bool
  posix_acl_xattr_list(struct dentry *dentry)

  {

  	return IS_POSIXACL(d_backing_inode(dentry));

  }
  
  const struct xattr_handler posix_acl_access_xattr_handler = {

  	.name = XATTR_NAME_POSIX_ACL_ACCESS,

  	.flags = ACL_TYPE_ACCESS,
  	.list = posix_acl_xattr_list,
  	.get = posix_acl_xattr_get,
  	.set = posix_acl_xattr_set,
  };
  EXPORT_SYMBOL_GPL(posix_acl_access_xattr_handler);
  
  const struct xattr_handler posix_acl_default_xattr_handler = {

  	.name = XATTR_NAME_POSIX_ACL_DEFAULT,

  	.flags = ACL_TYPE_DEFAULT,
  	.list = posix_acl_xattr_list,
  	.get = posix_acl_xattr_get,
  	.set = posix_acl_xattr_set,
  };
  EXPORT_SYMBOL_GPL(posix_acl_default_xattr_handler);

  
  int simple_set_acl(struct inode *inode, struct posix_acl *acl, int type)
  {
  	int error;
  
  	if (type == ACL_TYPE_ACCESS) {

  		error = posix_acl_update_mode(inode,
  				&inode->i_mode, &acl);
  		if (error)
  			return error;

  	}

  	inode->i_ctime = current_time(inode);

  	set_cached_acl(inode, type, acl);
  	return 0;
  }
  
  int simple_acl_create(struct inode *dir, struct inode *inode)
  {
  	struct posix_acl *default_acl, *acl;
  	int error;
  
  	error = posix_acl_create(dir, &inode->i_mode, &default_acl, &acl);
  	if (error)
  		return error;
  
  	set_cached_acl(inode, ACL_TYPE_DEFAULT, default_acl);
  	set_cached_acl(inode, ACL_TYPE_ACCESS, acl);
  
  	if (default_acl)
  		posix_acl_release(default_acl);
  	if (acl)
  		posix_acl_release(acl);
  	return 0;
  }