From owner-freebsd-current Thu Mar 4 17:32:56 1999 Delivered-To: freebsd-current@freebsd.org Received: from sand2.sentex.ca (sand2.sentex.ca [209.167.248.3]) by hub.freebsd.org (Postfix) with ESMTP id F0A0F150F8 for ; Thu, 4 Mar 1999 17:31:16 -0800 (PST) (envelope-from mike@sentex.net) Received: from gravel (ospf-wat.sentex.net [209.167.248.81]) by sand2.sentex.ca (8.8.8/8.8.8) with SMTP id UAA08535; Thu, 4 Mar 1999 20:30:55 -0500 (EST) (envelope-from mike@sentex.net) Message-Id: <4.1.19990304193540.08483b10@granite.sentex.ca> X-Sender: mdtancsa@granite.sentex.ca X-Mailer: QUALCOMM Windows Eudora Pro Version 4.1 Date: Thu, 04 Mar 1999 20:40:20 -0500 To: Matthew Dillon , Chris Costello From: Mike Tancsa Subject: Re: Simple DOS against 3.x locks box solid Cc: current@FreeBSD.ORG In-Reply-To: <199903050022.QAA32802@apollo.backplane.com> References: <4.1.19990304073656.084804e0@granite.sentex.ca> <19990304155401.A5710@holly.dyndns.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG 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