RE: [PATCH] /proc/pid/status: show all sets of pid according to ns

[chenhanxiao@xxxxxxxxxxxxxx]

Hi Vasily,

> -----Original Message-----
> From: Vasily Kulikov [mailto:segooon@xxxxxxxxx]
> Sent: Tuesday, May 27, 2014 2:05 AM
> To: Chen, Hanxiao/陈 晗霄
> Cc: containers@xxxxxxxxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Serge
> Hallyn; Oleg Nesterov; David Howells; Eric W. Biederman; Andrew Morton; Al Viro
> Subject: Re: [PATCH] /proc/pid/status: show all sets of pid according to ns
> 
> Hi Chen,
> 
> On Mon, May 26, 2014 at 18:05 +0800, Chen Hanxiao wrote:
> > We need a direct method of getting the pid inside containers.
> > If some issues occurred inside a container guest, host user
> > could not know which process is in trouble just by guest pid:
> > the users of container guest only knew the pid inside containers.
> > This will bring obstacle for trouble shooting.
> >
> > This patch expands fields of Tgid and Pid:
> > a) In init_pid_ns, nothing changed;
> >
> > b) In one pidns, they will tell the pid inside containers:
> > Tgid:	1628 	9 	3
> > Pid:	1628 	9 	3
> > ** process id is 1628 in level 0, 9 in level 1, 3 in level 2.
> 
> 1. It breaks ABI.  Any application which does something like "grep pid: | cut -d:
> -f2"
> is now broken by the patch.  Maybe add a new field like 'Pid-ns', 'PidNS',
> or 'Pids' and leave the old one for compatibility?
> 

Thanks for your comments.
Adding a new field could solve backward compatibility issue.

> 2. Is it OK to show internal pids to unprivileged processes?  I cannot
> see anything obviously dangerous with it, though.
> 

I thinks just 'showing' them would not bring some troubles.

> > c) If pidns is nested, it depends on which pidns are you in.
> > Tgid:	9 	3
> > Pid:	9 	3
> > ** Views from level 1 for Pid 1628 in host.
> 
> --
> Vasily

Thanks,
- Chen