text: // SPDX-License-Identifier: GPL-2.0
  /*
   * linux/fs/ext4/acl.c
   *
   * Copyright (C) 2001-2003 Andreas Gruenbacher, <agruen@suse.de>
   */
  
  #include <linux/quotaops.h>
  #include "ext4_jbd2.h"
  #include "ext4.h"
  #include "xattr.h"
  #include "acl.h"
  
  /*
   * Convert from filesystem to in-memory representation.
   */
  static struct posix_acl *
  ext4_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(ext4_acl_header))
  		 return ERR_PTR(-EINVAL);
  	if (((ext4_acl_header *)value)->a_version !=
  	    cpu_to_le32(EXT4_ACL_VERSION))
  		return ERR_PTR(-EINVAL);
  	value = (char *)value + sizeof(ext4_acl_header);
  	count = ext4_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++) {
  		ext4_acl_entry *entry =
  			(ext4_acl_entry *)value;
  		if ((char *)value + sizeof(ext4_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(ext4_acl_entry_short);
  			break;
  
  		case ACL_USER:
  			value = (char *)value + sizeof(ext4_acl_entry);
  			if ((char *)value > end)
  				goto fail;
  			acl->a_entries[n].e_uid =
  				make_kuid(&init_user_ns,
  					  le32_to_cpu(entry->e_id));
  			break;
  		case ACL_GROUP:
  			value = (char *)value + sizeof(ext4_acl_entry);
  			if ((char *)value > end)
  				goto fail;
  			acl->a_entries[n].e_gid =
  				make_kgid(&init_user_ns,
  					  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 *
  ext4_acl_to_disk(const struct posix_acl *acl, size_t *size)
  {
  	ext4_acl_header *ext_acl;
  	char *e;
  	size_t n;
  
  	*size = ext4_acl_size(acl->a_count);
  	ext_acl = kmalloc(sizeof(ext4_acl_header) + acl->a_count *
  			sizeof(ext4_acl_entry), GFP_NOFS);
  	if (!ext_acl)
  		return ERR_PTR(-ENOMEM);
  	ext_acl->a_version = cpu_to_le32(EXT4_ACL_VERSION);
  	e = (char *)ext_acl + sizeof(ext4_acl_header);
  	for (n = 0; n < acl->a_count; n++) {
  		const struct posix_acl_entry *acl_e = &acl->a_entries[n];
  		ext4_acl_entry *entry = (ext4_acl_entry *)e;
  		entry->e_tag  = cpu_to_le16(acl_e->e_tag);
  		entry->e_perm = cpu_to_le16(acl_e->e_perm);
  		switch (acl_e->e_tag) {
  		case ACL_USER:
  			entry->e_id = cpu_to_le32(
  				from_kuid(&init_user_ns, acl_e->e_uid));
  			e += sizeof(ext4_acl_entry);
  			break;
  		case ACL_GROUP:
  			entry->e_id = cpu_to_le32(
  				from_kgid(&init_user_ns, acl_e->e_gid));
  			e += sizeof(ext4_acl_entry);
  			break;
  
  		case ACL_USER_OBJ:
  		case ACL_GROUP_OBJ:
  		case ACL_MASK:
  		case ACL_OTHER:
  			e += sizeof(ext4_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
   */
  struct posix_acl *
  ext4_get_acl(struct inode *inode, int type, bool rcu)
  {
  	int name_index;
  	char *value = NULL;
  	struct posix_acl *acl;
  	int retval;
  
  	if (rcu)
  		return ERR_PTR(-ECHILD);
  
  	switch (type) {
  	case ACL_TYPE_ACCESS:
  		name_index = EXT4_XATTR_INDEX_POSIX_ACL_ACCESS;
  		break;
  	case ACL_TYPE_DEFAULT:
  		name_index = EXT4_XATTR_INDEX_POSIX_ACL_DEFAULT;
  		break;
  	default:
  		BUG();
  	}
  	retval = ext4_xattr_get(inode, name_index, "", NULL, 0);
  	if (retval > 0) {
  		value = kmalloc(retval, GFP_NOFS);
  		if (!value)
  			return ERR_PTR(-ENOMEM);
  		retval = ext4_xattr_get(inode, name_index, "", value, retval);
  	}
  	if (retval > 0)
  		acl = ext4_acl_from_disk(value, retval);
  	else if (retval == -ENODATA || retval == -ENOSYS)
  		acl = NULL;
  	else
  		acl = ERR_PTR(retval);
  	kfree(value);
  
  	return acl;
  }
  
  /*
   * Set the access or default ACL of an inode.
   *
   * inode->i_mutex: down unless called from ext4_new_inode
   */
  static int
  __ext4_set_acl(handle_t *handle, struct inode *inode, int type,
  	     struct posix_acl *acl, int xattr_flags)
  {
  	int name_index;
  	void *value = NULL;
  	size_t size = 0;
  	int error;
  
  	switch (type) {
  	case ACL_TYPE_ACCESS:
  		name_index = EXT4_XATTR_INDEX_POSIX_ACL_ACCESS;
  		break;
  
  	case ACL_TYPE_DEFAULT:
  		name_index = EXT4_XATTR_INDEX_POSIX_ACL_DEFAULT;
  		if (!S_ISDIR(inode->i_mode))
  			return acl ? -EACCES : 0;
  		break;
  
  	default:
  		return -EINVAL;
  	}
  	if (acl) {
  		value = ext4_acl_to_disk(acl, &size);
  		if (IS_ERR(value))
  			return (int)PTR_ERR(value);
  	}
  
  	error = ext4_xattr_set_handle(handle, inode, name_index, "",
  				      value, size, xattr_flags);
  
  	kfree(value);
  	if (!error)
  		set_cached_acl(inode, type, acl);
  
  	return error;
  }
  
  int
  ext4_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
  	     struct posix_acl *acl, int type)
  {
  	handle_t *handle;
  	int error, credits, retries = 0;
  	size_t acl_size = acl ? ext4_acl_size(acl->a_count) : 0;
  	umode_t mode = inode->i_mode;
  	int update_mode = 0;
  
  	error = dquot_initialize(inode);
  	if (error)
  		return error;
  retry:
  	error = ext4_xattr_set_credits(inode, acl_size, false /* is_create */,
  				       &credits);
  	if (error)
  		return error;
  
  	handle = ext4_journal_start(inode, EXT4_HT_XATTR, credits);
  	if (IS_ERR(handle))
  		return PTR_ERR(handle);
  	ext4_fc_start_update(inode);
  
  	if ((type == ACL_TYPE_ACCESS) && acl) {
  		error = posix_acl_update_mode(mnt_userns, inode, &mode, &acl);
  		if (error)
  			goto out_stop;
  		if (mode != inode->i_mode)
  			update_mode = 1;
  	}
  
  	error = __ext4_set_acl(handle, inode, type, acl, 0 /* xattr_flags */);
  	if (!error && update_mode) {
  		inode->i_mode = mode;
  		inode->i_ctime = current_time(inode);
  		error = ext4_mark_inode_dirty(handle, inode);
  	}
  out_stop:
  	ext4_journal_stop(handle);
  	ext4_fc_stop_update(inode);
  	if (error == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
  		goto retry;
  	return error;
  }
  
  /*
   * Initialize the ACLs of a new inode. Called from ext4_new_inode.
   *
   * dir->i_mutex: down
   * inode->i_mutex: up (access to inode is still exclusive)
   */
  int
  ext4_init_acl(handle_t *handle, struct inode *inode, struct inode *dir)
  {
  	struct posix_acl *default_acl, *acl;
  	int error;
  
  	error = posix_acl_create(dir, &inode->i_mode, &default_acl, &acl);
  	if (error)
  		return error;
  
  	if (default_acl) {
  		error = __ext4_set_acl(handle, inode, ACL_TYPE_DEFAULT,
  				       default_acl, XATTR_CREATE);
  		posix_acl_release(default_acl);
  	} else {
  		inode->i_default_acl = NULL;
  	}
  	if (acl) {
  		if (!error)
  			error = __ext4_set_acl(handle, inode, ACL_TYPE_ACCESS,
  					       acl, XATTR_CREATE);
  		posix_acl_release(acl);
  	} else {
  		inode->i_acl = NULL;
  	}
  	return error;
  }
  