long name_to_handle_at(int dfd, const char __user * name,
struct file_handle __user * handle, int flag)
{
int follow;
long ret = -EINVAL;
struct nameidata nd;
struct file *file = NULL;
if(!capable(CAP_DAC_OVERRIDE))
{
ret = -EPERM;
goto err_out;
}
if((flag & ~AT_SYMLINK_FOLLOW) != 0)
goto err_out;
if(name == NULL && dfd != AT_FDCWD)
{
file = fget(dfd);
if(file)
nd.dentry = file->f_dentry;
else
{
ret = -EBADF;
goto err_out;
}
}
else
{
follow = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0;
ret = __user_walk_fd(dfd, name, follow, &nd);
if(ret)
goto err_out;
}
ret = do_sys_name_to_handle(&nd, handle);
if(file)
fput(file);
else
path_release(&nd);
err_out:
return ret;
}
/**
* sys_name_to_handle_at: convert name to handle
* @dfd: directory relative to which name is interpreted if not absolute
* @name: name that should be converted to handle.
* @handle: resulting file handle
* @mnt_id: mount id of the file system containing the file
* @flag: flag value to indicate whether to follow symlink or not
*
* @handle->handle_size indicate the space available to store the
* variable part of the file handle in bytes. If there is not
* enough space, the field is updated to return the minimum
* value required.
*/
SYSCALL_DEFINE5(name_to_handle_at, int, dfd, const char __user *, name,
struct file_handle __user *, handle, int __user *, mnt_id,
int, flag)
{
struct path path;
int lookup_flags;
int err;
if ((flag & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
return -EINVAL;
lookup_flags = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0;
if (flag & AT_EMPTY_PATH)
lookup_flags |= LOOKUP_EMPTY;
err = user_path_at(dfd, name, lookup_flags, &path);
if (!err) {
err = do_sys_name_to_handle(&path, handle, mnt_id);
path_put(&path);
}
return err;
}
