Re: [RFC][PATCH 7/7][v2] Define clone_with_pids syscall

[Sukadev Bhattiprolu <sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>]

Oren Laadan [orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org] wrote:

| > +
| > +	if (num_pids < 0 || num_pids > task_pid(current)->level + 1)
| > +		return ERR_PTR(-EINVAL);
| 
| What happens if (num_pids < task_pid(current->level) + 1) ?
| Unless I missed something elsewhere, I suspect it will oops,

Yep. the kzalloc() below this check should use:

	task_pid(current)->pid_ns->level+1 * sizeof(pid_t)

| because in patch #4, you had:
| 
|  	for (i = ns->level; i >= 0; i--) {
| -		nr = alloc_pidmap(tmp, 0);
| +		tpid = 0;
| +		if (target_pids)
| +			tpid = target_pids[i];
| +
| +		nr = alloc_pidmap(tmp, tpid);
|  		if (nr < 0)
|  			goto out_free;
| 
| In general, can a task figure out it's depth in the pid-ns hierarchy ?
| 
| I'm thinking of a case in which a checkpoint was taken of a (flat)
| container which is in depth 2 of the global hierarchy, and then it
| is restarted in depth 3, or in depth 1.
| 
| Perhaps the semantics of the syscall should be that target_pids will
| indicate the desired pids _from the bottom up_. A value of "0" means

Hmm, I thought bottom up would be confusing, but I guess that would
work better :-) Will fix and resend.

| "don't care" and let the kernel assign. The remaining levels (upwards)
| will be treated as zeros.
| 
| [...]
| 
| Oren.
|