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    SubjectRe: [PATCH v10 05/11] seccomp: add system call filtering using BPF
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    On Wed, 2012-02-22 at 09:19 +0100, Indan Zupancic wrote:
    [...]
    > Alternative approach: Tell the arch at filter install time and only run the
    > filters with the same arch as the current system call. If no filters are run,
    > deny the systemcall.
    >
    > Advantages:
    >
    > - Filters don't have to check the arch every syscall entry.
    >
    > - Secure by default. Filters don't have to do anything arch specific to
    > be secure, no surprises possible.
    >
    > - If a new arch comes into existence, there is no chance of old filters
    > becoming buggy and insecure. This is especially true for archs that
    > had only one mode, but added another one later on: Old filters had no
    > need to check the mode at all.
    [...]

    What about when there are multiple layers of restrictions? So long as
    any one layer covers the new architecture, there is no default-deny even
    though the other layers might not cover it.

    I would have thought the way to make sure the architecture is always
    checked is to pack it together with the syscall number.

    Ben.

    --
    Ben Hutchings, Staff Engineer, Solarflare
    Not speaking for my employer; that's the marketing department's job.
    They asked us to note that Solarflare product names are trademarked.



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