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Re: [PATCH 11/13] Changes to show virtual ids to user [message #13636 is a reply to message #13635]

Thu, 31 May 2007 13:41

ebiederm
Messages: 1354
Registered: February 2006

Senior Member

Pavel Emelianov <xemul@openvz.org> writes:

> Eric W. Biederman wrote:
>> Pavel Emelianov <xemul@openvz.org> writes:
>>
>>> Pavel Emelianov wrote:
>>>> Cedric Le Goater wrote:
>>>>> Hello !
>>>>>
>>>>>>>> The worst case I can see with pid == 0. Is that it would be a bug
>>>>>>>> that we can fix later. For other cases it would seem to be a user
>>>>>>>> space API thing that we get stuck with for all time.
>>>>>>> We cannot trust userspace application to expect some pid other than
>>>>>>> positive. All that we can is either use some always-absent pid or
>>>>>>> send the signal as SI_KERNEL.
>>>>>>>
>>>>>>> Our experience show that making decisions like above causes random
>>>>> <>> applications failures that are hard (or even impossible) to debug.
>>>>>
>>>>>> Ok. So I guess I see what you are proposing is picking an arbitrary
>>>>>> pid, say pid == 2, and reserving that in all pid namespaces and using
>>>>>> it when we have a pid that does not map to a specific namespace. I'm
>>>>>> fine with that.
>>>>>>
>>>>>> All I care about is that we have a solution, preferably simple,
>>>>>> to the non-mapped pid problem.
>>>>> Pavel, are you against using pid == 0 and setting si_code to SI_KERNEL ?
>>>> I think I am. A quick grep through the code revealed one place where
>>> Sorry. I have misprinted. I meant "I think I am *NOT*". My bad :(
>>>
>>>> this can happen, so I believe application are (have to be) somehow
>>>> prepared to this.
>>
>> Where was this. I'd like to follow your complete line of thinking.
>
> The line concerning why I think that sending a signal from
> SI_KERNEL is good solution?

Let me just restate everything to be certain we are not getting
confused.

The problem was what to do with signals from unmmaped pids.

You have just said pid == 0 with SI_KERNEL seems to work.

The kernel occasionally sends signal that way already.

The primary argument against this in my memory was that we
a user space application might treat the kernel case special
(more trust), so it might be a bad idea.

I believe what you just said was that user space has to be ready
to handle signals from pid == 0 with SI_KERNEL set. Therefore this
should just work. I don't think you have addressed the levels of
trust in user space issue or I might be confused.

Eric

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[Message index]

		[PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Thu, 24 May 2007 12:32
		[PATCH 1/13] Round up the API By: Pavel Emelianov on Thu, 24 May 2007 12:35
		Re: [PATCH 1/13] Round up the API By: serue on Thu, 24 May 2007 16:09
		Re: [PATCH 1/13] Round up the API By: ebiederm on Thu, 24 May 2007 16:22
		Re: [PATCH 1/13] Round up the API By: Pavel Emelianov on Thu, 24 May 2007 16:31
		Re: [PATCH 1/13] Round up the API By: serue on Thu, 24 May 2007 16:48
		Re: [PATCH 1/13] Round up the API By: Pavel Emelianov on Fri, 25 May 2007 07:00
		Re: [PATCH 1/13] Round up the API By: serue on Fri, 25 May 2007 13:02
		[PATCH 2/13] Small preparations for namespaces By: Pavel Emelianov on Thu, 24 May 2007 12:37
		Re: [PATCH 2/13] Small preparations for namespaces By: serue on Thu, 24 May 2007 16:08
		Re: [PATCH 2/13] Small preparations for namespaces By: Pavel Emelianov on Fri, 25 May 2007 06:58
		Re: [PATCH 2/13] Small preparations for namespaces By: serue on Fri, 25 May 2007 13:01
		Re: [PATCH 2/13] Small preparations for namespaces By: Pavel Emelianov on Fri, 25 May 2007 13:21
		Re: [PATCH 2/13] Small preparations for namespaces By: serue on Fri, 25 May 2007 13:55
		[PATCH 3/13] Introduciton of config option and clone flag By: Pavel Emelianov on Thu, 24 May 2007 12:42
		Re: [PATCH 3/13] Introduciton of config option and clone flag By: ebiederm on Thu, 24 May 2007 15:39
		[PATCH 4/13] Introduce the vpid fields and helpers for getting them By: Pavel Emelianov on Thu, 24 May 2007 12:44
		[PATCH 5/13] Expand the pid/task seeking functions set By: Pavel Emelianov on Thu, 24 May 2007 12:46
		Re: [PATCH 5/13] Expand the pid/task seeking functions set By: Dave Hansen on Thu, 24 May 2007 17:11
		Re: [PATCH 5/13] Expand the pid/task seeking functions set By: Pavel Emelianov on Fri, 25 May 2007 07:08
		Re: [PATCH 5/13] Expand the pid/task seeking functions set By: Sukadev Bhattiprolu on Fri, 25 May 2007 23:36
		[PATCH 6/13] Pid allocation/freeing procedures By: Pavel Emelianov on Thu, 24 May 2007 12:49
		[PATCH 7/13] Set virtual pids for a newly cloned task By: Pavel Emelianov on Thu, 24 May 2007 12:53
		[PATCH 8/13] The namespace cloning By: Pavel Emelianov on Thu, 24 May 2007 12:57
		[PATCH 9/13] Make proc be able to have multiple super blocks By: Pavel Emelianov on Thu, 24 May 2007 13:01
		[PATCH 10/13] Make proc draw pids from appropriate namespace By: Pavel Emelianov on Thu, 24 May 2007 13:04
		[PATCH 11/13] Changes to show virtual ids to user By: Pavel Emelianov on Thu, 24 May 2007 13:06
		Re: [PATCH 11/13] Changes to show virtual ids to user By: ebiederm on Thu, 24 May 2007 16:05
		Re: [PATCH 11/13] Changes to show virtual ids to user By: xemul on Thu, 24 May 2007 16:15
		Re: [PATCH 11/13] Changes to show virtual ids to user By: ebiederm on Thu, 24 May 2007 16:33
		Re: [PATCH 11/13] Changes to show virtual ids to user By: Pavel Emelianov on Fri, 25 May 2007 06:33
		Re: [PATCH 11/13] Changes to show virtual ids to user By: ebiederm on Fri, 25 May 2007 15:48
		Re: [PATCH 11/13] Changes to show virtual ids to user By: Cedric Le Goater on Tue, 29 May 2007 12:32
		Re: [PATCH 11/13] Changes to show virtual ids to user By: Pavel Emelianov on Thu, 31 May 2007 07:57
		Re: [PATCH 11/13] Changes to show virtual ids to user By: Pavel Emelianov on Thu, 31 May 2007 08:00
		Re: [PATCH 11/13] Changes to show virtual ids to user By: ebiederm on Thu, 31 May 2007 11:26
		Re: [PATCH 11/13] Changes to show virtual ids to user By: Pavel Emelianov on Thu, 31 May 2007 11:46
		Re: [PATCH 11/13] Changes to show virtual ids to user By: ebiederm on Thu, 31 May 2007 13:41
		[PATCH 12/13] Show appropriate pids in proc By: Pavel Emelianov on Thu, 24 May 2007 13:08
		[PATCH 13/13] Make all proc entres accessible in a namespace By: Pavel Emelianov on Thu, 24 May 2007 13:13
		Instructions of how to make testing easy By: Pavel Emelianov on Thu, 24 May 2007 13:19
		Re: Instructions of how to make testing easy By: Pavel Emelianov on Thu, 24 May 2007 16:16
		Re: Instructions of how to make testing easy By: Cedric Le Goater on Thu, 24 May 2007 14:55
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: serue on Thu, 24 May 2007 15:09
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: xemul on Thu, 24 May 2007 16:11
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: serue on Thu, 24 May 2007 16:59
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: ebiederm on Thu, 24 May 2007 18:56
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: serue on Thu, 24 May 2007 19:10
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Fri, 25 May 2007 07:08
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: serue on Fri, 25 May 2007 13:25
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Fri, 25 May 2007 13:53
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: serue on Fri, 25 May 2007 14:25
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Mon, 28 May 2007 07:48
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: ebiederm on Tue, 29 May 2007 04:30
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Tue, 29 May 2007 07:47
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: ebiederm on Tue, 29 May 2007 12:36
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Fri, 25 May 2007 07:06
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: ebiederm on Fri, 25 May 2007 14:55
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: ebiederm on Thu, 24 May 2007 16:00
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: serue on Thu, 24 May 2007 16:20
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Fri, 25 May 2007 06:29
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: serue on Fri, 25 May 2007 13:29
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Thu, 24 May 2007 16:26
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: ebiederm on Thu, 24 May 2007 19:18
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Fri, 25 May 2007 07:15
		Re: Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: dev on Mon, 28 May 2007 11:50
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: ebiederm on Tue, 29 May 2007 13:07
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Daniel Lezcano on Thu, 24 May 2007 16:41
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Fri, 25 May 2007 07:26
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Daniel Lezcano on Fri, 25 May 2007 08:30

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