Re: Forking shell bombs

system_lists
2003-07-08T21:44:29Z

Hello,

Debian 3.0 (woody) stable. Kernel 2.4.21 ...
bash 2.05a

$ulimit -u
1791

---

No problems here. In 1-2 secs the process dies and all is ok, i can work
with the shell without any problem.

Seeya

At 16:43 08/07/2003 -0400, jhigdon wrote:
>Ryan Underwood wrote:
>
>>Hi,
>>
>>
>>
>>>That's what per-user process limits are for. Doesn't matter if it's a
>>>shellscript or something else; any system without limits set is
>>>vulnerable.
>>>
>>
>>I agree, but it would also be nice to have a way to clean up after the
>>fact without giving up the box. My limit is set at 2047 processes
>>which, while being a lot, doesn't seem like enough to guarantee a dead
>>box. (Don't many busy systems have more than this number running at any
>>given time?)
>>
>>
>>
>>>It's a base redhat kernel, after the cannot allocate memory, my system
>>>returned to normal operation and it didnt die.
>>>Is this the type of behavior you were looking for? or am i off base?
>>>
>>>Linux sloth 2.4.20-8 #1 Thu Mar 13 17:54:28 EST 2003 i686 i686 i386
>>>GNU/Linux
>>>
>>>$ :(){ :|:&};:
>>>[1] 3071
>>>
>>>$
>>>[1]+ Done : | :
>>>
>>>$ -bash: fork: Cannot allocate memory
>>>-bash: fork: Cannot allocate memory
>>>-bash: fork: Cannot allocate memory
>>>-bash: fork: Cannot allocate memory
>>>
>>
>>Nope, on my system running stock 2.4.21, after hitting enter, wait about 2
>>seconds, and the system is frozen. Telnet connects but never gets a
>>shell. None of the SysRq process-killing combos have any effect. After
>>a few failed killalls (which eventually killed the one shell I was able
>>to get), and Alt-SysRq-S never completing the sync, I gave up and
>>Alt-SysRq-B.
>>
>>What does ulimit -u say on your system? 2047 on mine.
>>
>>
>$ ulimit -u
>3072
>
>
>Have you tried this on any 2.5.x kernels? Just curious to see what it
>does, I plan on giving it a go later.
>
>
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