Re: [PATCH] ns: introduce getnspid syscall

[Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

On 06/17, Chen Hanxiao wrote:
>
> +SYSCALL_DEFINE4(getnspid, pid_t, pid, int, fd1, int, fd2, int, pidtype)
> +{
> +	struct file *file1 = NULL, *file2 = NULL;
> +	struct task_struct *task;
> +	struct pid_namespace *ns1, *ns2;
> +	struct proc_ns *ei;
> +	int ret = -1;
> +
> +	if (pidtype >= PIDTYPE_MAX)
> +		return -EINVAL;
> +
> +	file1 = proc_ns_fget(fd1);
> +	if (IS_ERR(file1))
> +		return PTR_ERR(file1);
> +	ei = get_proc_ns(file_inode(file1));
> +	ns1 = (struct pid_namespace *)ei->ns;

and I am not sure this part is correct... shouldn't we also verify that
ns_ops == pidns_operations ?

Perhaps it makes sense to generalize get_net_ns_by_fd() into
"void *get_ns_by_fd(fd, type)"... this probably needs another "check-and-get"
method in proc_ns_operations(). I dunno.

Oleg.