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

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Message-ID: <1288805913.2939.53.camel@localhost.localdomain>
Date:	Wed, 03 Nov 2010 13:38:33 -0400
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	Steve Grubb <sgrubb@...hat.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 Wed, 2010-11-03 at 13:00 -0400, Steve Grubb wrote:
> On Tuesday, October 12, 2010 09:40:34 am Mimi Zohar wrote:
> > On Tue, 2010-10-12 at 09:19 -0400, Steve Grubb wrote:
> > > On Tuesday, October 12, 2010 09:06:09 am Mimi Zohar wrote:
> > > > On Tue, 2010-10-12 at 14:14 +0300, Ozan Çağlayan wrote:
> > > > > Cuma 02 Temmuz 2010 günü (saat 03:16:01) James Morris şunları yazmıştı:
> > > > > > On Thu, 1 Jul 2010, Mimi Zohar wrote:
> > > > > > > Make the security extended attributes names global. Updated to
> > > > > > > move the remaining Smack xattrs.
> > > > > > > 
> > > > > > > Signed-off-by: Mimi Zohar <zohar@...ibm.com>
> > > > > > > Acked-by: Serge Hallyn <serue@...ibm.com>
> > > > > 
> > > > > This drops
> > > > > 
> > > > > #define XATTR_CAPS_SUFFIX "capability"
> > > > > #define XATTR_NAME_CAPS XATTR_SECURITY_PREFIX XATTR_CAPS_SUFFIX
> > > > > 
> > > > > definitions from capability.h and puts them in xattr.h's #ifdef
> > > > > __KERNEL__ section making them invisible to userspace like libcap-ng
> > > > > causing build failures.
> > > > > 
> > > > > Am I wrong?
> > > > 
> > > > You're correct.  It's the same reason that cap-ng.c has to define
> > > > 'security'.
> > > > 
> > > > #ifdef VFS_CAP_U32
> > > > 
> > > >  #include <attr/xattr.h>
> > > >  #define XATTR_SECURITY_PREFIX "security."
> > > > 
> > > > Am cc'ing Steve.
> > > 
> > > So does this mean I need to provide more definitions for libcap-ng to
> > > work with future kernels or are you asking my opinion? My opinion is
> > > that if user space needs it to work correctly, please let it be
> > > available so I don't have to make my own define which may be inaccurate
> > > one day.
> > > 
> > > Thanks,
> > > -Steve
> > 
> > Before making any changes to the kernel xattr.h, I want to understand
> > the reason for two xattr.h files, one in /usr/include/linux/ and the
> > other in /usr/include/xattr/.  /usr/include/linux/xattr.h contains those
> > elements not defined as __kernel__, while /usr/include/xattr/xattr.h
> > contains that and other definitions.  Will changing the kernel xattr.h
> > version change both?
> > 
> > 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).

Mimi

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