linux-kernel - Re: [PATCH 1/1] cgroups: implement device whitelist (v6)

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Message-ID: <20080329081839.GA4423@ucw.cz>
Date:	Sat, 29 Mar 2008 09:18:40 +0100
From:	Pavel Machek <pavel@....cz>
To:	"Serge E. Hallyn" <serue@...ibm.com>
Cc:	lkml <linux-kernel@...r.kernel.org>, daniel@...ac.com,
	lizf@...fujitsu.com, Pavel Emelyanov <xemul@...nvz.org>,
	Greg KH <greg@...ah.com>, Andrew Morton <akpm@...l.org>
Subject: Re: [PATCH 1/1] cgroups: implement device whitelist (v6)

On Wed 2008-03-26 13:05:43, Serge E. Hallyn wrote:
> (This is identical to the version I sent on Mar 19 in response to
> the comments by Daniel Hokka Zakrisson, which are the last
> comments I've gotten.)
> 
> Implement a cgroup to track and enforce open and mknod restrictions on device
> files.  A device cgroup associates a device access whitelist with each
> cgroup.  A whitelist entry has 4 fields.  'type' is a (all), c (char), or
> b (block).  'all' means it applies to all types and all major and minor
> numbers.  Major and minor are either an integer or * for all.
> Access is a composition of r (read), w (write), and m (mknod).
> 
> The root device cgroup starts with rwm to 'all'.  A child devcg gets
> a copy of the parent.  Admins can then remove devices from the
> whitelist or add new entries.  A child cgroup can never receive a
> device access which is denied its parent.  However when a device
> access is removed from a parent it will not also be removed from the
> child(ren).
> 
> An entry is added using devices.allow, and removed using
> devices.deny.  For instance
> 
> 	echo 'c 1:3 mr' > /cgroups/1/devices.allow
> 
> allows cgroup 1 to read and mknod the device usually known as
> /dev/null.  Doing
> 
> 	echo a > /cgroups/1/devices.deny

Can't you use selinux or something?

Or just fix the userland as this is for old-udev compatibility, only?
The interface is ugly...

> diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h
> index 1ddebfc..e287745 100644
> --- a/include/linux/cgroup_subsys.h
> +++ b/include/linux/cgroup_subsys.h
> @@ -42,3 +42,9 @@ SUBSYS(mem_cgroup)
>  #endif
>  
>  /* */
> +
> +#ifdef CONFIG_CGROUP_DEVICE
> +SUBSYS(devices)
> +#endif
> +
> +/* */

I don't know what this is, but it does not look like C...

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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