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John Johansen authored
Domain transition so far have been largely blocked by no new privs, unless the transition has been provably a subset of the previous confinement. There was a couple problems with the previous implementations, - transitions that weren't explicitly a stack but resulted in a subset of confinement were disallowed - confinement subsets were only calculated from the previous confinement instead of the confinement being enforced at the time of no new privs, so transitions would have to get progressively tighter. Fix this by detecting and storing a reference to the task's confinement at the "time" no new privs is set. This reference is then used to determine whether a transition is a subsystem of the confinement at the time no new privs was set. Unfortunately the implementation is less than ideal in that we have to detect no new privs after the fact when a task attempts a domain transition. This is adequate for the currently but will not work in a stacking situation where no new privs could be conceivably be set in both the "host" and in the container. Signed-off-by:
John Johansen <john.johansen@canonical.com>
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