Re: copy-up xattr (Re: [RFC][PATCH 00/73] Union Mount [ver #2])

From: J. R. Okajima
Date: Wed Mar 28 2012 - 10:51:54 EST

David Howells:
> That's not necessarily good enough. What if and LSM, say SELinux, is in
> force? Now SELinux will happily label the files for you - but there's a
> reasonable chance they won't be correct. OTOH, they may not be correct even
> if they are copied up.

Then what will happen (or should happen) in cp(1) for such cases?
Can the --preserve=context or xattr option handle it correctly?
If cp(1) can hanle it correctly, then union-mount may be able to behave
similarly, or make the internal copy-up operaion a totally isolated
userspace module.
If cp(1) cannot, then union-mount will not either. And union-mount
should delete the copied-up file after the xattr error, while cp(1) may
left the copied file.

Finally, the number of cases which copy-up xattr succeeds may not be so
many, and the situation is similar to cp(1) which copies a file between
different filesystems.

J. R. Okajima
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