Date: Wed, 22 Mar 2000 10:24:08 -0800 From: Alfred Perlstein <bright@wintelcom.net> To: "Ronald G. Minnich" <rminnich@lanl.gov> Cc: hackers@FreeBSD.ORG, linux-kernel@vger.rutgers.edu, Michael Lampe <Michael.Lampe@iwr.uni-heidelberg.de> Subject: Re: How a normal user can crash any linux system (fwd) Message-ID: <20000322102407.K7305@fw.wintelcom.net> In-Reply-To: <Pine.LNX.4.20.0003221027300.624-100000@mini.acl.lanl.gov>; from rminnich@lanl.gov on Wed, Mar 22, 2000 at 10:27:39AM -0700 References: <Pine.LNX.4.20.0003221027300.624-100000@mini.acl.lanl.gov>
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This is cross-posted to both linux-kernel and freebsd-hackers, please set your replies properly. > ---------- Forwarded message ---------- > Date: Wed, 22 Mar 2000 16:02:40 +0100 > From: Michael Lampe <Michael.Lampe@iwr.uni-heidelberg.de> > To: linux-kernel@vger.rutgers.edu > Subject: How a normal user can crash any linux system > > I found the following by accident playing with PVM. If you start the > 'gexample' from the examples directory with dimension=10000 and no of > tasks=32 on one machine, it becomes almost immediately completely un- > usable and begins with heavy swapping. Considering how much memory > would be necessary for this computation before starting it would have > avoided the trouble. > > So the processes go on allocating memory until physical memory and swap > is exhausted. At this point processes are killed and now things are > really > becoming interesting: One would expect that the misbehaving gexample > processes are killed or maybe other processes started by the same user. > > Actually random processes are killed: I've seen klogd, syslogd, cron, > gpm > and inetd disappear. In some cases the machine was unaccessible locally > as > well as remotely, but the kernel seemed to be still running -- ping > showed > the machine still up. > > Apart from the specific system processes that are killed, the problem > can be > reproduced under many different configurations. I have tried SuSE 6.0 > with > kernel 2.2.12, SuSE 6.2 with kernel 2.2.14, LinuxPPC R4/R5 (Red Hat 5.x > based) > with some recent 2.2.x kernels and finally the SuSE pre-release for PPC. > PVM > was 3.4.x. > > Any comments ???? > * Ronald G. Minnich <rminnich@lanl.gov> [000322 09:57] wrote: > anybody want to try this on -current? No, a normal user shouldn't be able to crash any unix box with proper limits in place, this local DoS only works if there are no limitations. Please people, this is a 20 year old trick that I'm really tired of hearing come up every other month. It's called a forkbomb with a twist, it's old, boring and doesn't affect people with properly configured systems. Please consult your Operating System's documentation on how to setup limits. If you want to know why random processes are sometimes killed then you need to buy and read an OS book. thanks, -- -Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org] To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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