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    SubjectRe: [AppArmor 38/45] AppArmor: Module and LSM hooks
    On Mon, 2007-06-04 at 16:30 +0200, Andreas Gruenbacher wrote:
    > On Monday 04 June 2007 15:12, Pavel Machek wrote:
    > > How will kernel work with very long paths? I'd suspect some problems,
    > > if path is 1MB long and I attempt to print it in /proc
    > > somewhere.
    > Pathnames are only used for informational purposes in the kernel, except in
    > AppArmor of course.

    I don't mean this as a flame, but isn't the above statement the very
    crux of this discussion? Why should AppArmor be different from the rest
    of the kernel in its usage of pathnames (basis for decisions vs.
    informational reporting to userspace)? And if it is ok for AppArmor to
    generate and use pathnames as its basis of decisions on each open, then
    is it also ok for audit, inotify, and others to use them in the same
    manner? If the audit developers or inotify developers had come with
    patches that used d_path or equivalent in the same manner as AppArmor,
    don't you think they would have gotten the same resistance? And if you
    are truly trying to create a mechanism (in AppArmor) that you can
    ultimately apply widely to the system (going beyond AppArmor's original
    limited focus on a small set of network-facing daemons), aren't you
    concerned about the implications of having to generate a pathname on
    each open just to decide what to do? Is this really the "path" you want
    to take ;)?

    Another question: it seems like the read-only bind mount folks gave up
    on propagating the vfsmounts down and switched to a rather different
    approach (checking near the entry points, using mount writer counters).
    So similarly, what makes AppArmor fundamentally different that it
    wouldn't take a similar approach to what they are doing vs. propagating
    the vfsmounts down? Or do you think they made the wrong choice? If so,

    Just trying to understand your position better...

    Stephen Smalley
    National Security Agency

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