[CRIU] [PATCH 1/5] files: Fix crossing unused and service fds of shared fd tables

[Cyrill Gorcunov]

On Wed, Jun 07, 2017 at 06:15:12PM +0300, Kirill Tkhai wrote:
> service_fd_id is id of a specific task, while other tasks
> in shared fd table group may have bigger id numbers.
> In this case given unused fd intersects with service fds
> of such tasks. This leads to undefined behaviour. Fix that.
> 
> Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
> +int service_fd_min_fd(struct pstree_item *item)
>  {
> -	return service_fd_rlim_cur - (SERVICE_FD_MAX - 1) - SERVICE_FD_MAX * service_fd_id;
> +	struct fdt *fdt = rsti(item)->fdt;
> +	int id = 0;
> +
> +	if (fdt)
> +		id = fdt->nr - 1;

Why -1 here?