Date: Thu, 04 Mar 1999 20:40:20 -0500 From: Mike Tancsa <mike@sentex.net> To: Matthew Dillon <dillon@apollo.backplane.com>, Chris Costello <chris@holly.dyndns.org> Cc: current@FreeBSD.ORG Subject: Re: Simple DOS against 3.x locks box solid Message-ID: <4.1.19990304193540.08483b10@granite.sentex.ca> In-Reply-To: <199903050022.QAA32802@apollo.backplane.com> References: <4.1.19990304073656.084804e0@granite.sentex.ca> <19990304155401.A5710@holly.dyndns.org>
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At 07:22 PM 3/4/99 , Matthew Dillon wrote: > 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. Interesting... I thought there was something else going on, because when I walk back to the machine, the drive is not even spinning. I will have to wait until I go to the office to try it, as I need to physically reboot the unit if it 'works'... If it is the /proc issue, what would be the safest way to proctect against it ? Also, it does not take many iterations to lock up the machine. Three will do it. To limit that via login.access would hose most users. ---Mike ********************************************************************** 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
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