Messages in this thread | | | Date | Mon, 10 Feb 2014 20:51:33 +0100 | From | "Serge E. Hallyn" <> | Subject | overlayfs mounts in user namespaces |
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Hi Eric,
most filesystems cannot be mounted in a non-init user namespace because we don't trust the superblock parsers to DTRT when handed garbage. I was wondering if you had any ideas on ways that allowing root in a non-init userns to mount an overlayfs fs would be dangerous? There's no superblock parsing in that case at all; writes end up being allowed if and only if the userid owning the 'upper' (writeable) layer is mapped into the userns. Near as I can tell it should be quite safe. But my imagination isn't the most active.
I assume there would be concerns about memory usage if the system is not configured to place all logged-in users into configured cgroups? Is there anything else you can think of that could be abused?
(I realize overlayfs isn't upstream yet so the question may not be all that interesting to most people...)
thanks, -serge
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