linux-kernel - Re: [RFC][PATCH 3/5] Determine if sender is from ancestor ns+

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Date:	Thu, 4 Dec 2008 13:45:11 +0100
From:	Bastian Blank <bastian@...di.eu.org>
To:	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
Cc:	oleg@...hat.com, ebiederm@...ssion.com, roland@...hat.com,
	containers@...ts.osdl.org, linux-kernel@...r.kernel.org,
	xemul@...nvz.org
Subject: Re: [RFC][PATCH 3/5] Determine if sender is from ancestor ns+

On Tue, Dec 02, 2008 at 11:59:04AM -0800, Sukadev Bhattiprolu wrote:
> Bastian Blank [bastian@...di.eu.org] wrote:
> | sys_rt_sigqueueinfo disallows setting si_code to any value which
> | describes kernel signals from userspace. So using SI_FROMUSER should be
> | sufficient.
> SI_ASYNCIO qualifies as SI_FROMUSER() even when it originates from
> kernel (usb/core/devio.c async_completed())...

SI_ASYNCIO currently qualifies as user signal, it is sent in the context
of the pid issuing the async io request. It is never used as a kernel
originated signal in any way. The code sending it even seems to do a
full permission check.

If you think this is wrong, maybe this should be fixed first.

> If we know that it came from rt_sigqueueinfo(), we can safely check
> the namespace. If it came from driver we should skip the ns check.

If it have a sender pid attached, this should be checked.

> Yes, (Eric Biederman, Dec 2007)
> 	https://lists.linux-foundation.org/pipermail/containers/2007-December/009152.html
> Oleg Nesterov, Aug 2007:
> 	http://marc.info/?l=linux-kernel&m=118753610515859
> I had sent out a summary of the above attempts to Containers list recently:
> 	https://lists.linux-foundation.org/pipermail/containers/2008-November/013991.html

Okay.

> | Please add a complete comment to the function which describes the
> | function. And don't us "it" for not defined entities.
> Ah, I see the problem now. The 't' refers to the task parameter - how
> about changing comment to:

No, I meant a real comment, defining the complete behaviour, each
parameter with constraints and the possible return values.

Bastian

-- 
Insufficient facts always invite danger.
		-- Spock, "Space Seed", stardate 3141.9
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