linux-kernel - Re: [PATCH] Security/sysfs: Enable security xattrs to be set on sysfs files, directories, and symlinks.

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Message-ID: <20090714203522.GA18330@suse.de>
Date:	Tue, 14 Jul 2009 13:35:22 -0700
From:	Greg KH <gregkh@...e.de>
To:	"David P. Quigley" <dpquigl@...ho.nsa.gov>
Cc:	jmorris@...ei.org, sds@...ho.nsa.gov, linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org
Subject: Re: [PATCH] Security/sysfs: Enable security xattrs to be set on
 sysfs files, directories, and symlinks.

On Tue, Jul 14, 2009 at 04:16:06PM -0400, David P. Quigley wrote:
> On Tue, 2009-07-14 at 10:50 -0700, Greg KH wrote:
> > On Tue, Jul 14, 2009 at 12:37:39PM -0400, David P. Quigley wrote:
> > > So, I've been looking through the sysfs code and I can't find a
> > > reference to netlink in there. I am assuming that it is other parts of
> > > the kernel which make use of netlink which are calling the sysfs_*
> > > functions. Any suggestions for where to look on how this is being used
> > > and what the important users are?
> > 
> > The netlink messages are coming from the kobject uevent code, look in
> > lib/kobject_uevent.c for the code that creates and sends them out.  This
> > happens for every sysfs directory that is created that corresponds with
> > a kobject.
> > 
> > thanks,
> > 
> > greg k-h
> 
> It is unclear to me what if anything we need to do to the kobject_uevent
> code for these changes. Do you have a particular use case in mind? Is
> there some sort of notification that should be sent up to user space
> when the label is changed on a file?

No, the point is that userspace is notified when a kobject is created
and added to sysfs.  You can use that notification to then put the
"correct" label on the sysfs directory and files, if they differ from
your "default" value you wanted them to have.

Hope this helps,

greg k-h
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