Messages in this thread | | | Date | Thu, 16 Nov 2000 16:01:07 +0100 (MET) | From | Szabolcs Szakacsits <> | Subject | RE: KPATCH] Reserve VM for root (was: Re: Looking for better VM) |
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On Wed, 1 Jan 1997 pavel-velo@bug.ucw.cz wrote:
> >main() { while(1) if (fork()) malloc(1); } > >With the patch below I could ssh to the host and killall the offending > >processes. To enable reserving VM space for root do > what about main() { while(1) system("ftp localhost &"); } > This. or so,ething similar should allow you to kill your machine > even with your patch from normal user account
This or something similar didn't kill the box [I've tried all local DoS from Packetstorm that I could find]. Please send a working example. Of course probably it's possible to trigger root owned processes to eat memory eagerly by user apps but that's a problem in the process design running as root and not a kernel issue.
Note, I'm not discussing "local user can kill the box without limits", I say Linux "deadlocks" [it starts its own autonom life and usually your only chance is to hit the reset button] when there is continuous VM pressure by user applications. If you think fork() kills the box then ulimit the maximum number of user processes (ulimit -u). This is a different issue and a bad design in the scheduler (see e.g. Tru64 for a better one).
BTW, I have a new version of the patch with that Linux behaves much better from root's point of view when the memory is more significantly overcommited. I'll post it if I have time [and there is interest].
Szaka
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