[gentoo-hardened] SElinux+XFS

[Tad]

For anyone that is interested, I've created a patch to XFS that adds the
security.* extended attribute namespace needed by SElinux.

I've created two patches.
This (http://www.glines.com/xfs.patch.bz2) contains only the changes too
XFS.
This (http://www.glines.com/2.4.21-xfs+selinux.patch.bz2) can be applied
against a vanilla 2.4.21 kernel and will give you SElinux and a SElinux
friendly XFS.

Internally XFS distinguishes between user and trusted attributes via a flag
(XFS_ATTR_ROOT). If just modified xfs_iops.c is modified, the security.*
attributes also appear in the user.* namespace. I saw two ways fix this.

One option was to store the security.* attributes in either the trusted or
user namespace. Then hack the XFS internals so that any user.security.* or
trusted.security.* attribute would not appear in trusted or user but would
appear as if it was in the security namespace. I didn't like this option
because it was going to be a more complicated code chage. That, and it just
felt like a hack.

The other option was to add true support for the security namespace. This
would require adding a flag to the attribute's flags bitfield. I liked this
option because it was simpler to code and just looked cleaner. The bit slot
I chose appears to be unused. At least I could find no place in the code
that uses it. If security.* attributes are set and the filesystem is then
mounted with a standard XFS kernel, those attributes will appear in the user
namespace.

I haven't looked at xfsdump/xfsrestore so I don't know if they will require
changes. I'm hoping that they take the flags field whole and don't do
anything with it that could disrupt the new XFS_ATTR_SECURITY bit.

-Tad 


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