Re: [PATCH] 2.6.23: Filesystem capabilities 0.17

[Olaf Dietsche <olaf+list.linux-kernel@olafdietsche.de>]

Casey Schaufler <casey@schaufler-ca.com> writes:

> --- Olaf Dietsche <olaf+list.linux-kernel@olafdietsche.de> wrote:
>
>> The bits are stored in a sparse file named /.capabilities in the
>> directory of the mount point, where the corresponding executable
>> lives. The inode number of the file is the index into this file.
>
> The old PlanG approach. It's the way that we did MAC labels in
> Trix4. It has the wicked advantage of working across NFS without
> anyone being the wiser.

If you don't trust a NFS, you'll mount it nosuid anyway and then
fscaps are disabled too.

> It really causes trouble for backup utilities, however.

Whatever implementation you choose, you will always have to modify
your backup utilities or copy the attributes separately.

> Trix6 (there wasn't really a Trix5) had xattrs
> available and we found the switch well worth the investment.

Extended attributes are a nice, clean concept, like micro kernels for
example :-). But they have a cost, which shouldn't be ignored.

Regards, Olaf.