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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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