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    SubjectRe: [patch 0/4] MAP_NOZERO v2 - VM_NOZERO/MAP_NOZERO early summer madness
    On Sat, Jun 30, 2007 at 08:21:52PM -0400, Kyle Moffett wrote:
    > That's why you'd need to call an LSM hook to get a unique identifier,
    > as the LSM would actually need to allocate identifiers for
    > equivalence classes. Secondly, processes may change labels as they
    > run, so you couldn't just call it once and cache the result, you
    > would need to call it for every freed page (or every re-use of a page).

    Davide's patch adds a owner_uid field to mm_struct. Assuming that turns
    into a "mm security equivalence class identifier", the LSM can simply
    update it when a label-change-event occurs. No need to call out to
    (potentially heavyweight!) LSM code in page allocation critical paths.

    I'm a bit concerned that tracking the equivalence classes will get
    expensive. I think you can end up with quadratic explosion in the worst
    case (every user using every permutation of LSM bits).

    -andy
    -
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