text: /*
   * linux/fs/ext3/acl.c
   *
   * Copyright (C) 2001-2003 Andreas Gruenbacher, <agruen@suse.de>
   */
  
  #include <linux/init.h>
  #include <linux/sched.h>
  #include <linux/slab.h>
  #include <linux/capability.h>
  #include <linux/fs.h>
  #include <linux/ext3_jbd.h>
  #include <linux/ext3_fs.h>
  #include "xattr.h"
  #include "acl.h"
  
  /*
   * Convert from filesystem to in-memory representation.
   */
  static struct posix_acl *
  ext3_acl_from_disk(const void *value, size_t size)
  {
  	const char *end = (char *)value + size;
  	int n, count;
  	struct posix_acl *acl;
  
  	if (!value)
  		return NULL;
  	if (size < sizeof(ext3_acl_header))
  		 return ERR_PTR(-EINVAL);
  	if (((ext3_acl_header *)value)->a_version !=
  	    cpu_to_le32(EXT3_ACL_VERSION))
  		return ERR_PTR(-EINVAL);
  	value = (char *)value + sizeof(ext3_acl_header);
  	count = ext3_acl_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);
  	for (n=0; n < count; n++) {
  		ext3_acl_entry *entry =
  			(ext3_acl_entry *)value;
  		if ((char *)value + sizeof(ext3_acl_entry_short) > end)
  			goto fail;
  		acl->a_entries[n].e_tag  = le16_to_cpu(entry->e_tag);
  		acl->a_entries[n].e_perm = le16_to_cpu(entry->e_perm);
  		switch(acl->a_entries[n].e_tag) {
  			case ACL_USER_OBJ:
  			case ACL_GROUP_OBJ:
  			case ACL_MASK:
  			case ACL_OTHER:
  				value = (char *)value +
  					sizeof(ext3_acl_entry_short);
  				acl->a_entries[n].e_id = ACL_UNDEFINED_ID;
  				break;
  
  			case ACL_USER:
  			case ACL_GROUP:
  				value = (char *)value + sizeof(ext3_acl_entry);
  				if ((char *)value > end)
  					goto fail;
  				acl->a_entries[n].e_id =
  					le32_to_cpu(entry->e_id);
  				break;
  
  			default:
  				goto fail;
  		}
  	}
  	if (value != end)
  		goto fail;
  	return acl;
  
  fail:
  	posix_acl_release(acl);
  	return ERR_PTR(-EINVAL);
  }
  
  /*
   * Convert from in-memory to filesystem representation.
   */
  static void *
  ext3_acl_to_disk(const struct posix_acl *acl, size_t *size)
  {
  	ext3_acl_header *ext_acl;
  	char *e;
  	size_t n;
  
  	*size = ext3_acl_size(acl->a_count);
  	ext_acl = kmalloc(sizeof(ext3_acl_header) + acl->a_count *
  			sizeof(ext3_acl_entry), GFP_NOFS);
  	if (!ext_acl)
  		return ERR_PTR(-ENOMEM);
  	ext_acl->a_version = cpu_to_le32(EXT3_ACL_VERSION);
  	e = (char *)ext_acl + sizeof(ext3_acl_header);
  	for (n=0; n < acl->a_count; n++) {
  		ext3_acl_entry *entry = (ext3_acl_entry *)e;
  		entry->e_tag  = cpu_to_le16(acl->a_entries[n].e_tag);
  		entry->e_perm = cpu_to_le16(acl->a_entries[n].e_perm);
  		switch(acl->a_entries[n].e_tag) {
  			case ACL_USER:
  			case ACL_GROUP:
  				entry->e_id =
  					cpu_to_le32(acl->a_entries[n].e_id);
  				e += sizeof(ext3_acl_entry);
  				break;
  
  			case ACL_USER_OBJ:
  			case ACL_GROUP_OBJ:
  			case ACL_MASK:
  			case ACL_OTHER:
  				e += sizeof(ext3_acl_entry_short);
  				break;
  
  			default:
  				goto fail;
  		}
  	}
  	return (char *)ext_acl;
  
  fail:
  	kfree(ext_acl);
  	return ERR_PTR(-EINVAL);
  }
  
  /*
   * Inode operation get_posix_acl().
   *
   * inode->i_mutex: don't care
   */
  static struct posix_acl *
  ext3_get_acl(struct inode *inode, int type)
  {
  	int name_index;
  	char *value = NULL;
  	struct posix_acl *acl;
  	int retval;
  
  	if (!test_opt(inode->i_sb, POSIX_ACL))
  		return NULL;
  
  	acl = get_cached_acl(inode, type);
  	if (acl != ACL_NOT_CACHED)
  		return acl;
  
  	switch (type) {
  	case ACL_TYPE_ACCESS:
  		name_index = EXT3_XATTR_INDEX_POSIX_ACL_ACCESS;
  		break;
  	case ACL_TYPE_DEFAULT:
  		name_index = EXT3_XATTR_INDEX_POSIX_ACL_DEFAULT;
  		break;
  	default:
  		BUG();
  	}
  
  	retval = ext3_xattr_get(inode, name_index, "", NULL, 0);
  	if (retval > 0) {
  		value = kmalloc(retval, GFP_NOFS);
  		if (!value)
  			return ERR_PTR(-ENOMEM);
  		retval = ext3_xattr_get(inode, name_index, "", value, retval);
  	}
  	if (retval > 0)
  		acl = ext3_acl_from_disk(value, retval);
  	else if (retval == -ENODATA || retval == -ENOSYS)
  		acl = NULL;
  	else
  		acl = ERR_PTR(retval);
  	kfree(value);
  
  	if (!IS_ERR(acl))
  		set_cached_acl(inode, type, acl);
  
  	return acl;
  }
  
  /*
   * Set the access or default ACL of an inode.
   *
   * inode->i_mutex: down unless called from ext3_new_inode
   */
  static int
  ext3_set_acl(handle_t *handle, struct inode *inode, int type,
  	     struct posix_acl *acl)
  {
  	int name_index;
  	void *value = NULL;
  	size_t size = 0;
  	int error;
  
  	if (S_ISLNK(inode->i_mode))
  		return -EOPNOTSUPP;
  
  	switch(type) {
  		case ACL_TYPE_ACCESS:
  			name_index = EXT3_XATTR_INDEX_POSIX_ACL_ACCESS;
  			if (acl) {
  				mode_t mode = inode->i_mode;
  				error = posix_acl_equiv_mode(acl, &mode);
  				if (error < 0)
  					return error;
  				else {
  					inode->i_mode = mode;
  					inode->i_ctime = CURRENT_TIME_SEC;
  					ext3_mark_inode_dirty(handle, inode);
  					if (error == 0)
  						acl = NULL;
  				}
  			}
  			break;
  
  		case ACL_TYPE_DEFAULT:
  			name_index = EXT3_XATTR_INDEX_POSIX_ACL_DEFAULT;
  			if (!S_ISDIR(inode->i_mode))
  				return acl ? -EACCES : 0;
  			break;
  
  		default:
  			return -EINVAL;
  	}
  	if (acl) {
  		value = ext3_acl_to_disk(acl, &size);
  		if (IS_ERR(value))
  			return (int)PTR_ERR(value);
  	}
  
  	error = ext3_xattr_set_handle(handle, inode, name_index, "",
  				      value, size, 0);
  
  	kfree(value);
  
  	if (!error)
  		set_cached_acl(inode, type, acl);
  
  	return error;
  }
  
  int
  ext3_check_acl(struct inode *inode, int mask)
  {
  	struct posix_acl *acl = ext3_get_acl(inode, ACL_TYPE_ACCESS);
  
  	if (IS_ERR(acl))
  		return PTR_ERR(acl);
  	if (acl) {
  		int error = posix_acl_permission(inode, acl, mask);
  		posix_acl_release(acl);
  		return error;
  	}
  
  	return -EAGAIN;
  }
  
  /*
   * Initialize the ACLs of a new inode. Called from ext3_new_inode.
   *
   * dir->i_mutex: down
   * inode->i_mutex: up (access to inode is still exclusive)
   */
  int
  ext3_init_acl(handle_t *handle, struct inode *inode, struct inode *dir)
  {
  	struct posix_acl *acl = NULL;
  	int error = 0;
  
  	if (!S_ISLNK(inode->i_mode)) {
  		if (test_opt(dir->i_sb, POSIX_ACL)) {
  			acl = ext3_get_acl(dir, ACL_TYPE_DEFAULT);
  			if (IS_ERR(acl))
  				return PTR_ERR(acl);
  		}
  		if (!acl)
  			inode->i_mode &= ~current_umask();
  	}
  	if (test_opt(inode->i_sb, POSIX_ACL) && acl) {
  		struct posix_acl *clone;
  		mode_t mode;
  
  		if (S_ISDIR(inode->i_mode)) {
  			error = ext3_set_acl(handle, inode,
  					     ACL_TYPE_DEFAULT, acl);
  			if (error)
  				goto cleanup;
  		}
  		clone = posix_acl_clone(acl, GFP_NOFS);
  		error = -ENOMEM;
  		if (!clone)
  			goto cleanup;
  
  		mode = inode->i_mode;
  		error = posix_acl_create_masq(clone, &mode);
  		if (error >= 0) {
  			inode->i_mode = mode;
  			if (error > 0) {
  				/* This is an extended ACL */
  				error = ext3_set_acl(handle, inode,
  						     ACL_TYPE_ACCESS, clone);
  			}
  		}
  		posix_acl_release(clone);
  	}
  cleanup:
  	posix_acl_release(acl);
  	return error;
  }
  
  /*
   * Does chmod for an inode that may have an Access Control List. The
   * inode->i_mode field must be updated to the desired value by the caller
   * before calling this function.
   * Returns 0 on success, or a negative error number.
   *
   * We change the ACL rather than storing some ACL entries in the file
   * mode permission bits (which would be more efficient), because that
   * would break once additional permissions (like  ACL_APPEND, ACL_DELETE
   * for directories) are added. There are no more bits available in the
   * file mode.
   *
   * inode->i_mutex: down
   */
  int
  ext3_acl_chmod(struct inode *inode)
  {
  	struct posix_acl *acl, *clone;
          int error;
  
  	if (S_ISLNK(inode->i_mode))
  		return -EOPNOTSUPP;
  	if (!test_opt(inode->i_sb, POSIX_ACL))
  		return 0;
  	acl = ext3_get_acl(inode, ACL_TYPE_ACCESS);
  	if (IS_ERR(acl) || !acl)
  		return PTR_ERR(acl);
  	clone = posix_acl_clone(acl, GFP_KERNEL);
  	posix_acl_release(acl);
  	if (!clone)
  		return -ENOMEM;
  	error = posix_acl_chmod_masq(clone, inode->i_mode);
  	if (!error) {
  		handle_t *handle;
  		int retries = 0;
  
  	retry:
  		handle = ext3_journal_start(inode,
  				EXT3_DATA_TRANS_BLOCKS(inode->i_sb));
  		if (IS_ERR(handle)) {
  			error = PTR_ERR(handle);
  			ext3_std_error(inode->i_sb, error);
  			goto out;
  		}
  		error = ext3_set_acl(handle, inode, ACL_TYPE_ACCESS, clone);
  		ext3_journal_stop(handle);
  		if (error == -ENOSPC &&
  		    ext3_should_retry_alloc(inode->i_sb, &retries))
  			goto retry;
  	}
  out:
  	posix_acl_release(clone);
  	return error;
  }
  
  /*
   * Extended attribute handlers
   */
  static size_t
  ext3_xattr_list_acl_access(struct inode *inode, char *list, size_t list_len,
  			   const char *name, size_t name_len)
  {
  	const size_t size = sizeof(POSIX_ACL_XATTR_ACCESS);
  
  	if (!test_opt(inode->i_sb, POSIX_ACL))
  		return 0;
  	if (list && size <= list_len)
  		memcpy(list, POSIX_ACL_XATTR_ACCESS, size);
  	return size;
  }
  
  static size_t
  ext3_xattr_list_acl_default(struct inode *inode, char *list, size_t list_len,
  			    const char *name, size_t name_len)
  {
  	const size_t size = sizeof(POSIX_ACL_XATTR_DEFAULT);
  
  	if (!test_opt(inode->i_sb, POSIX_ACL))
  		return 0;
  	if (list && size <= list_len)
  		memcpy(list, POSIX_ACL_XATTR_DEFAULT, size);
  	return size;
  }
  
  static int
  ext3_xattr_get_acl(struct inode *inode, int type, void *buffer, size_t size)
  {
  	struct posix_acl *acl;
  	int error;
  
  	if (!test_opt(inode->i_sb, POSIX_ACL))
  		return -EOPNOTSUPP;
  
  	acl = ext3_get_acl(inode, type);
  	if (IS_ERR(acl))
  		return PTR_ERR(acl);
  	if (acl == NULL)
  		return -ENODATA;
  	error = posix_acl_to_xattr(acl, buffer, size);
  	posix_acl_release(acl);
  
  	return error;
  }
  
  static int
  ext3_xattr_get_acl_access(struct inode *inode, const char *name,
  			  void *buffer, size_t size)
  {
  	if (strcmp(name, "") != 0)
  		return -EINVAL;
  	return ext3_xattr_get_acl(inode, ACL_TYPE_ACCESS, buffer, size);
  }
  
  static int
  ext3_xattr_get_acl_default(struct inode *inode, const char *name,
  			   void *buffer, size_t size)
  {
  	if (strcmp(name, "") != 0)
  		return -EINVAL;
  	return ext3_xattr_get_acl(inode, ACL_TYPE_DEFAULT, buffer, size);
  }
  
  static int
  ext3_xattr_set_acl(struct inode *inode, int type, const void *value,
  		   size_t size)
  {
  	handle_t *handle;
  	struct posix_acl *acl;
  	int error, retries = 0;
  
  	if (!test_opt(inode->i_sb, POSIX_ACL))
  		return -EOPNOTSUPP;
  	if (!is_owner_or_cap(inode))
  		return -EPERM;
  
  	if (value) {
  		acl = posix_acl_from_xattr(value, size);
  		if (IS_ERR(acl))
  			return PTR_ERR(acl);
  		else if (acl) {
  			error = posix_acl_valid(acl);
  			if (error)
  				goto release_and_out;
  		}
  	} else
  		acl = NULL;
  
  retry:
  	handle = ext3_journal_start(inode, EXT3_DATA_TRANS_BLOCKS(inode->i_sb));
  	if (IS_ERR(handle))
  		return PTR_ERR(handle);
  	error = ext3_set_acl(handle, inode, type, acl);
  	ext3_journal_stop(handle);
  	if (error == -ENOSPC && ext3_should_retry_alloc(inode->i_sb, &retries))
  		goto retry;
  
  release_and_out:
  	posix_acl_release(acl);
  	return error;
  }
  
  static int
  ext3_xattr_set_acl_access(struct inode *inode, const char *name,
  			  const void *value, size_t size, int flags)
  {
  	if (strcmp(name, "") != 0)
  		return -EINVAL;
  	return ext3_xattr_set_acl(inode, ACL_TYPE_ACCESS, value, size);
  }
  
  static int
  ext3_xattr_set_acl_default(struct inode *inode, const char *name,
  			   const void *value, size_t size, int flags)
  {
  	if (strcmp(name, "") != 0)
  		return -EINVAL;
  	return ext3_xattr_set_acl(inode, ACL_TYPE_DEFAULT, value, size);
  }
  
  struct xattr_handler ext3_xattr_acl_access_handler = {
  	.prefix	= POSIX_ACL_XATTR_ACCESS,
  	.list	= ext3_xattr_list_acl_access,
  	.get	= ext3_xattr_get_acl_access,
  	.set	= ext3_xattr_set_acl_access,
  };
  
  struct xattr_handler ext3_xattr_acl_default_handler = {
  	.prefix	= POSIX_ACL_XATTR_DEFAULT,
  	.list	= ext3_xattr_list_acl_default,
  	.get	= ext3_xattr_get_acl_default,
  	.set	= ext3_xattr_set_acl_default,
  };
  