automatic garbage collection of stuff mounted (etc.) by jailed root

[Jamie Gritton]

On 04/22/13 03:17, Mateusz Guzik wrote:
> Hello,
>
> This is something that imho could be done by GSoC student.
>
> It is possible to allow jailed root to mount various filesystems. But
> once all processes are dead, mounts done by jailed root that he didn't
> clean up are still hanging around.
>
> As time passes and more stuff gets jailable we should expect problems
> like this in different subsystems.
>
> So I propose that someone(tm) implements a solution which cleans this
> stuff during jail destruction.
>
> One idea how to do it: implement a list with clean up operations. Using
> mount example: you add a filesystem to be cleaned up after it is
> mounted, you delete it after it is unmounted. When the jail is going to
> die you just traverse the list backwareds and call cleaning functions,
> in this case unmounting filesystems. Maybe this is is a bad idea in the
> first place and it is better to take a look at mount tree and traverse
> that, I don't know, you should investigate. :) Note that the code has to
> be robust in case of errors (e.g. given fs may not be unmountable
> because someone from prison0 is inside).
>
> Again, the goal is to have jails clean up automatically after anything
> jailed root was permitted to do.
>
> Thoughts?

This already happens when jails are created using a jail.conf file. Any
mounts there are unmounted as part of the jail removal process. Just
recently I fixed it to properly do this unmounting in reverse order.

- Jamie