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    SubjectRe: Dumping /dev/zero to the console
       From: lilo <TaRDiS@mail.utexas.edu>
    Date: Sun, 21 Jul 1996 10:44:25 -0500 (CDT)

    /dev/zero can be used for a variety of things. It contains no sensitive
    information (only binary zeroes :) and hence conceptually its access should
    not be restricted.

    There are a lot of other denial-of-service attacks that users can employ on
    Linux. If there's any interest in reducing the effectiveness of
    denial-of-service attacks (and improving Linux's handling of
    resource-exhaustion situations) that might be a better approach than simply
    denying access to this device.

    It's also not hard thwart fix this sort of denial-of-service attack;
    just put in code to periodically check to see if need_resched is true,
    and call schedule() to yield control of the process. You should also
    check to see if a signal has been posted, and exit appropriately:

    if (need_resched)
    schedule();
    if (current->signal & ~current->blocked)
    return (bytes_written ? bytes_written : -ERESTARTSYS);

    Any kernel system call which might be long-lived should definitely be
    doing something like this, just for robustness's sake.

    - Ted


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