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    SubjectRe: [RFC] syscalls, x86: Add __NR_kcmp syscall
    (1/18/12 6:57 AM), Cyrill Gorcunov wrote:
    > On Wed, Jan 18, 2012 at 04:23:24AM -0500, KOSAKI Motohiro wrote:
    >> (1/18/12 4:19 AM), Pavel Emelyanov wrote:
    >>>> I think Eric only said gt/lt compare is useful. We don't need to expose bare
    >>>> pointer order. example, kcmp(rotate(ptr, per-task-random-value)) is enough
    >>>> hide the critical information. I think.
    >>> The per-task might break thinks up in case
    >>> (tsk1->file != tsk2->file)&& (rotate(tsk1->file, tsk1->random) == rotate(tsk2->file, tsk2->rotate))
    >> I meant,
    >> (tsk1->file != tsk2->file)&& (rotate(tsk1->file, caller_task->random) == rotate(tsk2->file, caller_task->random))
    >>> but I agree, that the overall idea of comparing not bare pointers, but those poisoned with
    >>> some global value can address the Peter's concerns about rootkits.
    > Guys, can we stick with something simplier? I could use hashes here (again?!) or
    > even aes encoded pointers extended to 128 bits as it was proposed too. But
    > maybe we can live with something more simplier?

    The problem of hashes is,

    - SHA1 didn't provide correct "equal or not" policy. (and I don't think sha1 is faster than kcmp)
    - Poisoned pointer can be used to restore original bare pointer.

    Do this have the same issue?

    > We could export EQ/NE for regular users (which might be usefull for less
    > frequently used objects such as namespaces I guess). And GT/LT for root
    > only.
    > Does it look better? Does the change log tells enough?

    I dislike. Just EQ/NE is better than "root only" behavior change. it's misleading.
    If you dislike GT/LT, please just delete it.

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      Last update: 2012-01-18 17:49    [W:0.028 / U:158.760 seconds]
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