From owner-freebsd-current Thu Mar 4 16:22:39 1999 Delivered-To: freebsd-current@freebsd.org Received: from apollo.backplane.com (apollo.backplane.com [209.157.86.2]) by hub.freebsd.org (Postfix) with ESMTP id 5DE66150C0 for ; Thu, 4 Mar 1999 16:22:38 -0800 (PST) (envelope-from dillon@apollo.backplane.com) Received: (from dillon@localhost) by apollo.backplane.com (8.9.3/8.9.1) id QAA32802; Thu, 4 Mar 1999 16:22:19 -0800 (PST) (envelope-from dillon) Date: Thu, 4 Mar 1999 16:22:19 -0800 (PST) From: Matthew Dillon Message-Id: <199903050022.QAA32802@apollo.backplane.com> To: Chris Costello Cc: Mike Tancsa , current@FreeBSD.ORG Subject: Re: Simple DOS against 3.x locks box solid References: <4.1.19990304073656.084804e0@granite.sentex.ca> <19990304155401.A5710@holly.dyndns.org> Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Well, 10 processes doing a find are not supposed to lockup a machine. However, there is another potential problem with the script below ... if the script is run as root, the find will cross mount points including the /proc mount point. Now running xargs and random process's memory spaces *could* certainly lockup a machine. /proc does has reentrancy issue with multiple processes accessing it at the same time. Try changing the 'find' to 'find -x'. If this still locks up the machine we will have to then determine whether it occurs under 4.x as well, or if it only occurs under 3.x. -Matt Matthew Dillon :On Thu, Mar 4, 1999, Mike Tancsa put this into my mailbox: :> :> Is there any way to stop what is below ? : : Yep. Don't do it! : : Seriously, though, that puts a major load on the system. : : You have 10 process all telling the drivers to keep seeking :about through the disks. : : Add /etc/login.conf restrictions if you don't want your users :to do that. : :> :> :> :> As posted by yk@dgtu.donetsk.ua :> > :> >This script freeze my 3.1-RELEASE box. :> >I can't make any connection with my box, also from console. :> > :> >-------- cut here --- :> >#! /bin/sh :> > :> >for j in 1 2 3 4 5 6 7 8 9 10 :> >do :> >echo -n $j :> >nohup sh -c 'while :; do find / -type file |xargs fgrep fticom; done' :> >/dev/null 2>&1 & :> >echo :> >done :> >--------- cut here ---- :> > :> >-- :> >Yury V. Yaroshevsky | Donetsk State Technical University :> >YY18-RIPE | (380 622) 356455 yk@dgtu.donetsk.ua :> > :> ********************************************************************** :> Mike Tancsa, Network Admin * mike@sentex.net :> Sentex Communications Corp, * http://www.sentex.net/mike :> Cambridge, Ontario * 01.519.651.3400 :> Canada * :> :> :> To Unsubscribe: send mail to majordomo@FreeBSD.org :> with "unsubscribe freebsd-current" in the body of the message :> : :-- :Powered by FreeBSD 4.0-CURRENT. "The Power to Serve!" To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message