Messages in this thread | | | From | Michael Buesch <> | Subject | Re: Forking shell bombs | Date | Wed, 9 Jul 2003 13:36:03 +0200 |
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On Tuesday 08 July 2003 22:28, 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.
mb@lfs:~> ulimit -u 2047
my system doesn't freeze. It becomes _very_ slow, but I can kill the forking processes. After killing, the system runs just fine. I'm using 2.4.21.
- -- Regards Michael Buesch http://www.8ung.at/tuxsoft 13:34:31 up 12 min, 2 users, load average: 1.32, 1.22, 0.74
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