linux-kernel - Re: [PATCH] core_pattern: set core helpers root and namespace to crashing process

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Message-Id: <20121213142534.ea07a3c8.akpm@linux-foundation.org>
Date:	Thu, 13 Dec 2012 14:25:34 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Neil Horman <nhorman@...driver.com>
Cc:	Serge Hallyn <serge.hallyn@...onical.com>,
	linux-kernel@...r.kernel.org,
	Daniel Berrange <berrange@...hat.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	containers@...ts.linux-foundation.org
Subject: Re: [PATCH] core_pattern: set core helpers root and namespace to
 crashing process

On Thu, 13 Dec 2012 13:12:20 -0500
Neil Horman <nhorman@...driver.com> wrote:

> On Thu, Dec 13, 2012 at 06:20:48AM -0600, Serge Hallyn wrote:
> > Quoting Neil Horman (nhorman@...driver.com):
> > > Theres one problem I currently see with it, and that is that I'm not sure we can
> > > change the current behavior of how the root fs is set for the pipe reader, lest
> > > we break some user space expectations. As such, I've added a sysctl in this
> > > patch to allow administrators to globally select if a core reader specified via
> > > /proc/sys/kernel/core_pattern should use the global rootfs, or the (possibly)
> > > chrooted fs of the crashing process.
> > 
> > Practical question:  How is the admin to make an educated decision on
> > how to set the sysctl?

By reading the documentation which Neil didn't include?

> My thought was that the admin typically wouldn't touch this at all.  I really
> added it as a backwards compatibility option only.  Setting the user space
> helper task to the root of the crashing parent has the possibility of breaking
> existing installs because the core_pattern helper might be expecting global file
> system access.  Moving forward, my expectation would be that core_pattern
> helpers would be written with the default setting in mind, and we could
> eventually deprecate the control entirely.
> 
> If you have a better mechanism in mind however (or if you think that removing
> the control is a resaonable approach), I'm certainly open to that.

Yeah, this is a tiresome patch but I can't think of a better way.

Except, perhaps, adding a new token to the core_pattern which says
"switch namespaces"?

Is there any propect that the core_pattern itself will later become a
per-namespace containerised thing?  I guess that if the per-container
core_pattern has been configured, we can implicitly do the namespace
switch as well.

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