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    SubjectRe: [PATCH 3/7] seccomp_filter: Enable ftrace-based system call filtering
    Quoting Will Drewry (wad@chromium.org):
    > My intent was to make them available for use by seccomp.c during state
    > teardown/dup. I don't think there's benefit to exposing them outside
    > of that. Would dropping the export, and adding an local seccomp.h
    > with the shared functions in them resolve that more cleanly?

    And add a clear comment explaining :)

    > > Your code would have been correct if you could call kzalloc under
    > > rcu_read_lock() (which you can on some kernel configurations but not
    > > all). The issue is that you need to pull out that allocation from the
    > > rcu_read_lock() because rcu_read_lock assumes you can't preempt, and
    > > that allocation can schedule out. The access to the filters must be done
    > > under rcu_read_lock(), other than that, you're fine.
    >
    > That makes sense. I think I'd prefer to not share those functions
    > rather than guard the list just in case a future consumer of the
    > interface comes along. Would that make sense to you? Since I don't
    > see any other users right now other than seccomp.c, it might make
    > sense to tackle the impact when an actual need arises.
    >
    > I'll go whichever way pointed on this, though.

    Complicating the locking for nonexistent users doesn't seem like the
    right way.

    -serge


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