linux-kernel - Re: [PATCH] security: move LSM xattrnames to xattr.h

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Date:	Wed, 3 Nov 2010 13:57:37 -0400
From:	Steve Grubb <sgrubb@...hat.com>
To:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc:	Ozan Çağlayan <ozan@...dus.org.tr>,
	James Morris <jmorris@...ei.org>, linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	Casey Schaufler <casey@...aufler-ca.com>,
	David Safford <safford@...son.ibm.com>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Mimi Zohar <zohar@...ibm.com>
Subject: Re: [PATCH] security: move LSM xattrnames to xattr.h

On Wednesday, November 03, 2010 01:38:33 pm Mimi Zohar wrote:
> > > As long as we're making this change, should 'security' also be defined
> > > outside of the __kernel__ definitions?
> >
> > I guess no one fixed this before 2.6.36 was finalized. Removing the
> > define has broke user  space compilation for anything that works on file
> > based capabilities. I can define it myself, but if the kernel folks ever
> > change the string, then we have more than just a compile problem, we
> > have runtime problems because I can no longer use the correct string.
> >
> > So, what was the gain for breaking user space?
> >
> > -Steve
> 
> Sorry I dropped the ball. Was expecting some kind of response to my
> question above, and then forgot about it.
> 
> All of the 'security' xattrs were moved to fsmagic.h, including
> capability. Not only those that EVM protects, but others like
> XATTR_NAME_SMACKIPIN/OUT (based on Casey's request).

If user space has to know the exact contents of a string in order to do something that 
the kernel understands, then its part of a public API. I've made my own define and 
released a new copy of libcap-ng. So, if the contents of the string ever change, or 
becomes deprecated, you'll now have user space apps using the old values no matter 
what.

-Steve
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