Re: fork()

From: Triffid Hunter
Date: Thu Mar 24 2005 - 13:18:22 EST


you can limit the max number of processes by putting the following into /etc/security/limits.conf (on my distro, and quite a number of others according to google too)

* hard nproc <max # processes>

you can also limit quite a number of other things in this file, and other files in that directory.

redoubtable wrote:
Hey,

I read a document on securityfocus about fork bombinb a linux system. Although they didn't speak about the effectiveness of resource limits I guess that should be discussed because it's possible to make a linux machine extremely slow (compared to FreeBSD for instance) even with well configured resource limits.
I revised kernel/fork.c and I found a way to prevent this problem by removing all associated processes with the parent, but that's far from portable and should not be used for the sake of compatibilities. I guess the function fork() should be revised.
And what about creating a 'maxprocs' sysctl var (even if left high) when the resource limits problem is fixed? It would help security when it is needed and wouldn't bother other applications. RLIMITs on login are not trustworthy. It should exist a global limit in case someone could spawn a shell without limits through some flawed application.

Thanks, and please advise.

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