[pups] User Mode DoS Attacks (was Re: Issues of AUUGN)
Johnny Billquist
bqt at softjar.se
Fri Oct 6 00:44:36 AEST 2006
Back in those days, there didn't exist any process limits, except for
system wide ones... :-)
Another fun exercise that actually hurts systems today, but didn't hurt
much back then, are programs that allocate a large chunk of memory and
hit on a single address on each page repetedly.
Talk about thrashing the memory system... :-) But on the PDP-11, you
don't use demand paging, nor can you allocate that much memory.
Johnny
Bill Gunshannon wrote:
>>>But you'd need kernel mode for that; this is a DoS attack (one of the
>>>first?) launched by a user.
>>
>>The userland DoS I remember:
>>
>>main() {
>> while(1)
>> fork();
>>}
>
>
> Typical "Rabbit Program".
>
>
>>And in fact I tried it once on the 11/45 I had access to. Not pretty.
>>It can be made less disastrous by judicious addition of a wait(); call.
>>
>>--Milo, wondering how contemporary UNIX will deal with such
>>pathological behavior....
>
>
> Not necessarily pathological. I have students do it all the time
> in the early parts of the Operating Systems Course. The only one
> it denies service to on contemorary UNIX is the individual who does
> it. Process limits are by user, not by system.
>
> bill
>
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