xattr.c

linux 内核源代码

      out_dir:
	fput(fp);

      out:
	attrs->ia_valid = ia_valid;
	return err;
}

/* Actual operations that are exported to VFS-land */

/*
 * Inode operation getxattr()
 * Preliminary locking: we down dentry->d_inode->i_mutex
 */
ssize_t
reiserfs_getxattr(struct dentry * dentry, const char *name, void *buffer,
		  size_t size)
{
	struct reiserfs_xattr_handler *xah = find_xattr_handler_prefix(name);
	int err;

	if (!xah || !reiserfs_xattrs(dentry->d_sb) ||
	    get_inode_sd_version(dentry->d_inode) == STAT_DATA_V1)
		return -EOPNOTSUPP;

	reiserfs_read_lock_xattr_i(dentry->d_inode);
	reiserfs_read_lock_xattrs(dentry->d_sb);
	err = xah->get(dentry->d_inode, name, buffer, size);
	reiserfs_read_unlock_xattrs(dentry->d_sb);
	reiserfs_read_unlock_xattr_i(dentry->d_inode);
	return err;
}

/*
 * Inode operation setxattr()
 *
 * dentry->d_inode->i_mutex down
 */
int
reiserfs_setxattr(struct dentry *dentry, const char *name, const void *value,
		  size_t size, int flags)
{
	struct reiserfs_xattr_handler *xah = find_xattr_handler_prefix(name);
	int err;
	int lock;

	if (!xah || !reiserfs_xattrs(dentry->d_sb) ||
	    get_inode_sd_version(dentry->d_inode) == STAT_DATA_V1)
		return -EOPNOTSUPP;

	reiserfs_write_lock_xattr_i(dentry->d_inode);
	lock = !has_xattr_dir(dentry->d_inode);
	if (lock)
		reiserfs_write_lock_xattrs(dentry->d_sb);
	else
		reiserfs_read_lock_xattrs(dentry->d_sb);
	err = xah->set(dentry->d_inode, name, value, size, flags);
	if (lock)
		reiserfs_write_unlock_xattrs(dentry->d_sb);
	else
		reiserfs_read_unlock_xattrs(dentry->d_sb);
	reiserfs_write_unlock_xattr_i(dentry->d_inode);
	return err;
}

/*
 * Inode operation removexattr()
 *
 * dentry->d_inode->i_mutex down
 */
int reiserfs_removexattr(struct dentry *dentry, const char *name)
{
	int err;
	struct reiserfs_xattr_handler *xah = find_xattr_handler_prefix(name);

	if (!xah || !reiserfs_xattrs(dentry->d_sb) ||
	    get_inode_sd_version(dentry->d_inode) == STAT_DATA_V1)
		return -EOPNOTSUPP;

	reiserfs_write_lock_xattr_i(dentry->d_inode);
	reiserfs_read_lock_xattrs(dentry->d_sb);

	/* Deletion pre-operation */
	if (xah->del) {
		err = xah->del(dentry->d_inode, name);
		if (err)
			goto out;
	}

	err = reiserfs_xattr_del(dentry->d_inode, name);

	dentry->d_inode->i_ctime = CURRENT_TIME_SEC;
	mark_inode_dirty(dentry->d_inode);

      out:
	reiserfs_read_unlock_xattrs(dentry->d_sb);
	reiserfs_write_unlock_xattr_i(dentry->d_inode);
	return err;
}

/* This is what filldir will use:
 * r_pos will always contain the amount of space required for the entire
 * list. If r_pos becomes larger than r_size, we need more space and we
 * return an error indicating this. If r_pos is less than r_size, then we've
 * filled the buffer successfully and we return success */
struct reiserfs_listxattr_buf {
	int r_pos;
	int r_size;
	char *r_buf;
	struct inode *r_inode;
};

static int
reiserfs_listxattr_filler(void *buf, const char *name, int namelen,
			  loff_t offset, u64 ino, unsigned int d_type)
{
	struct reiserfs_listxattr_buf *b = (struct reiserfs_listxattr_buf *)buf;
	int len = 0;
	if (name[0] != '.'
	    || (namelen != 1 && (name[1] != '.' || namelen != 2))) {
		struct reiserfs_xattr_handler *xah =
		    find_xattr_handler_prefix(name);
		if (!xah)
			return 0;	/* Unsupported xattr name, skip it */

		/* We call ->list() twice because the operation isn't required to just
		 * return the name back - we want to make sure we have enough space */
		len += xah->list(b->r_inode, name, namelen, NULL);

		if (len) {
			if (b->r_pos + len + 1 <= b->r_size) {
				char *p = b->r_buf + b->r_pos;
				p += xah->list(b->r_inode, name, namelen, p);
				*p++ = '\0';
			}
			b->r_pos += len + 1;
		}
	}

	return 0;
}

/*
 * Inode operation listxattr()
 *
 * Preliminary locking: we down dentry->d_inode->i_mutex
 */
ssize_t reiserfs_listxattr(struct dentry * dentry, char *buffer, size_t size)
{
	struct file *fp;
	struct dentry *dir;
	int err = 0;
	struct reiserfs_listxattr_buf buf;

	if (!dentry->d_inode)
		return -EINVAL;

	if (!reiserfs_xattrs(dentry->d_sb) ||
	    get_inode_sd_version(dentry->d_inode) == STAT_DATA_V1)
		return -EOPNOTSUPP;

	reiserfs_read_lock_xattr_i(dentry->d_inode);
	reiserfs_read_lock_xattrs(dentry->d_sb);
	dir = open_xa_dir(dentry->d_inode, FL_READONLY);
	reiserfs_read_unlock_xattrs(dentry->d_sb);
	if (IS_ERR(dir)) {
		err = PTR_ERR(dir);
		if (err == -ENODATA)
			err = 0;	/* Not an error if there aren't any xattrs */
		goto out;
	}

	fp = dentry_open(dir, NULL, O_RDWR);
	if (IS_ERR(fp)) {
		err = PTR_ERR(fp);
		/* dentry_open dputs the dentry if it fails */
		goto out;
	}

	buf.r_buf = buffer;
	buf.r_size = buffer ? size : 0;
	buf.r_pos = 0;
	buf.r_inode = dentry->d_inode;

	REISERFS_I(dentry->d_inode)->i_flags |= i_has_xattr_dir;

	err = xattr_readdir(fp, reiserfs_listxattr_filler, &buf);
	if (err)
		goto out_dir;

	if (buf.r_pos > buf.r_size && buffer != NULL)
		err = -ERANGE;
	else
		err = buf.r_pos;

      out_dir:
	fput(fp);

      out:
	reiserfs_read_unlock_xattr_i(dentry->d_inode);
	return err;
}

/* This is the implementation for the xattr plugin infrastructure */
static struct list_head xattr_handlers = LIST_HEAD_INIT(xattr_handlers);
static DEFINE_RWLOCK(handler_lock);

static struct reiserfs_xattr_handler *find_xattr_handler_prefix(const char
								*prefix)
{
	struct reiserfs_xattr_handler *xah = NULL;
	struct list_head *p;

	read_lock(&handler_lock);
	list_for_each(p, &xattr_handlers) {
		xah = list_entry(p, struct reiserfs_xattr_handler, handlers);
		if (strncmp(xah->prefix, prefix, strlen(xah->prefix)) == 0)
			break;
		xah = NULL;
	}

	read_unlock(&handler_lock);
	return xah;
}

static void __unregister_handlers(void)
{
	struct reiserfs_xattr_handler *xah;
	struct list_head *p, *tmp;

	list_for_each_safe(p, tmp, &xattr_handlers) {
		xah = list_entry(p, struct reiserfs_xattr_handler, handlers);
		if (xah->exit)
			xah->exit();

		list_del_init(p);
	}
	INIT_LIST_HEAD(&xattr_handlers);
}

int __init reiserfs_xattr_register_handlers(void)
{
	int err = 0;
	struct reiserfs_xattr_handler *xah;
	struct list_head *p;

	write_lock(&handler_lock);

	/* If we're already initialized, nothing to do */
	if (!list_empty(&xattr_handlers)) {
		write_unlock(&handler_lock);
		return 0;
	}

	/* Add the handlers */
	list_add_tail(&user_handler.handlers, &xattr_handlers);
	list_add_tail(&trusted_handler.handlers, &xattr_handlers);
#ifdef CONFIG_REISERFS_FS_SECURITY
	list_add_tail(&security_handler.handlers, &xattr_handlers);
#endif
#ifdef CONFIG_REISERFS_FS_POSIX_ACL
	list_add_tail(&posix_acl_access_handler.handlers, &xattr_handlers);
	list_add_tail(&posix_acl_default_handler.handlers, &xattr_handlers);
#endif

	/* Run initializers, if available */
	list_for_each(p, &xattr_handlers) {
		xah = list_entry(p, struct reiserfs_xattr_handler, handlers);
		if (xah->init) {
			err = xah->init();
			if (err) {
				list_del_init(p);
				break;
			}
		}
	}

	/* Clean up other handlers, if any failed */
	if (err)
		__unregister_handlers();

	write_unlock(&handler_lock);
	return err;
}

void reiserfs_xattr_unregister_handlers(void)
{
	write_lock(&handler_lock);
	__unregister_handlers();
	write_unlock(&handler_lock);
}

/* This will catch lookups from the fs root to .reiserfs_priv */
static int
xattr_lookup_poison(struct dentry *dentry, struct qstr *q1, struct qstr *name)
{
	struct dentry *priv_root = REISERFS_SB(dentry->d_sb)->priv_root;
	if (name->len == priv_root->d_name.len &&
	    name->hash == priv_root->d_name.hash &&
	    !memcmp(name->name, priv_root->d_name.name, name->len)) {
		return -ENOENT;
	} else if (q1->len == name->len &&
		   !memcmp(q1->name, name->name, name->len))
		return 0;
	return 1;
}

static struct dentry_operations xattr_lookup_poison_ops = {
	.d_compare = xattr_lookup_poison,
};

/* We need to take a copy of the mount flags since things like
 * MS_RDONLY don't get set until *after* we're called.
 * mount_flags != mount_options */
int reiserfs_xattr_init(struct super_block *s, int mount_flags)
{
	int err = 0;

	/* We need generation numbers to ensure that the oid mapping is correct
	 * v3.5 filesystems don't have them. */
	if (!old_format_only(s)) {
		set_bit(REISERFS_XATTRS, &(REISERFS_SB(s)->s_mount_opt));
	} else if (reiserfs_xattrs_optional(s)) {
		/* Old format filesystem, but optional xattrs have been enabled
		 * at mount time. Error out. */
		reiserfs_warning(s, "xattrs/ACLs not supported on pre v3.6 "
				 "format filesystem. Failing mount.");
		err = -EOPNOTSUPP;
		goto error;
	} else {
		/* Old format filesystem, but no optional xattrs have been enabled. This
		 * means we silently disable xattrs on the filesystem. */
		clear_bit(REISERFS_XATTRS, &(REISERFS_SB(s)->s_mount_opt));
	}

	/* If we don't have the privroot located yet - go find it */
	if (reiserfs_xattrs(s) && !REISERFS_SB(s)->priv_root) {
		struct dentry *dentry;
		dentry = lookup_one_len(PRIVROOT_NAME, s->s_root,
					strlen(PRIVROOT_NAME));
		if (!IS_ERR(dentry)) {
			if (!(mount_flags & MS_RDONLY) && !dentry->d_inode) {
				struct inode *inode = dentry->d_parent->d_inode;
				mutex_lock_nested(&inode->i_mutex,
						  I_MUTEX_XATTR);
				err = inode->i_op->mkdir(inode, dentry, 0700);
				mutex_unlock(&inode->i_mutex);
				if (err) {
					dput(dentry);
					dentry = NULL;
				}

				if (dentry && dentry->d_inode)
					reiserfs_warning(s,
							 "Created %s on %s - reserved for "
							 "xattr storage.",
							 PRIVROOT_NAME,
							 reiserfs_bdevname
							 (inode->i_sb));
			} else if (!dentry->d_inode) {
				dput(dentry);
				dentry = NULL;
			}
		} else
			err = PTR_ERR(dentry);

		if (!err && dentry) {
			s->s_root->d_op = &xattr_lookup_poison_ops;
			reiserfs_mark_inode_private(dentry->d_inode);
			REISERFS_SB(s)->priv_root = dentry;
		} else if (!(mount_flags & MS_RDONLY)) {	/* xattrs are unavailable */
			/* If we're read-only it just means that the dir hasn't been
			 * created. Not an error -- just no xattrs on the fs. We'll
			 * check again if we go read-write */
			reiserfs_warning(s, "xattrs/ACLs enabled and couldn't "
					 "find/create .reiserfs_priv. Failing mount.");
			err = -EOPNOTSUPP;
		}
	}

      error:
	/* This is only nonzero if there was an error initializing the xattr
	 * directory or if there is a condition where we don't support them. */
	if (err) {
		clear_bit(REISERFS_XATTRS, &(REISERFS_SB(s)->s_mount_opt));
		clear_bit(REISERFS_XATTRS_USER, &(REISERFS_SB(s)->s_mount_opt));
		clear_bit(REISERFS_POSIXACL, &(REISERFS_SB(s)->s_mount_opt));
	}

	/* The super_block MS_POSIXACL must mirror the (no)acl mount option. */
	s->s_flags = s->s_flags & ~MS_POSIXACL;
	if (reiserfs_posixacl(s))
		s->s_flags |= MS_POSIXACL;

	return err;
}

static int reiserfs_check_acl(struct inode *inode, int mask)
{
	struct posix_acl *acl;
	int error = -EAGAIN; /* do regular unix permission checks by default */

	reiserfs_read_lock_xattr_i(inode);
	reiserfs_read_lock_xattrs(inode->i_sb);

	acl = reiserfs_get_acl(inode, ACL_TYPE_ACCESS);

	reiserfs_read_unlock_xattrs(inode->i_sb);
	reiserfs_read_unlock_xattr_i(inode);

	if (acl) {
		if (!IS_ERR(acl)) {
			error = posix_acl_permission(inode, acl, mask);
			posix_acl_release(acl);
		} else if (PTR_ERR(acl) != -ENODATA)
			error = PTR_ERR(acl);
	}

	return error;
}

int reiserfs_permission(struct inode *inode, int mask, struct nameidata *nd)
{
	/*
	 * We don't do permission checks on the internal objects.
	 * Permissions are determined by the "owning" object.
	 */
	if (is_reiserfs_priv_object(inode))
		return 0;

	/*
	 * Stat data v1 doesn't support ACLs.
	 */
	if (get_inode_sd_version(inode) == STAT_DATA_V1)
		return generic_permission(inode, mask, NULL);
	else
		return generic_permission(inode, mask, reiserfs_check_acl);
}