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    SubjectRe: [PATCH 0/4] Checkpoint/Restore: Show in proc IDs of objects that can be shared between tasks
    On Tue, Nov 15, 2011 at 09:44:27PM -0800, Matt Helsley wrote:
    ...
    > >
    > > The object address is XOR-ed with a "random" value of the same size and then
    > > shown in proc. Providing this poison is not leaked into the userspace then
    > > ID seem to be safe.
    >
    > Really? There's no way to quickly derive the random number from known
    > allocation patterns and thereby break the obfuscation scheme?
    > To start we can note that the low N bits are directly exposed in the ID
    > of anything that requires 2^N-byte alignment.
    >
    > I think it's really a question of whether the high order bits can be derived.
    >

    Good point. I suppose we might use 2 random numbers here, one for xor and
    second to shuffle bits.

    > And of course the random number only needs to be derived once per boot
    > before it reveals the address of everything with an ID.

    Cyrill


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