Date: Thu, 10 May 2001 08:59:11 +0800 From: "David Xu" <bsddiy@163.net> To: "Pete Fritchman" <petef@databits.net>, <freebsd-questions@freebsd.org> Subject: Re: kenel panic, vm_map_entry_create: kernel resources exhausted Message-ID: <002301c0d8ec$ae4df540$3601a8c0@xyf> References: <002f01c0d840$5ed38180$3601a8c0@xyf> <20010509131701.F72871@databits.net>
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Hi,
do you really think about this problem carefully ?
due to lack of information about maxusers and RAM size,
how many maxusers an administrator can config for his RAM size?
it needn't a fork bomb to crash system, think about a heavy loaded
system,
when processes number is increased, pmap table resource will possible
be exhausted, and the bug will be trigged. an login.conf is bogus for
this case,
it can not prevent system from crash. I am very unhappy with this weak
design, vm just does not protect itself. suck! :(
---
Regards,
David Xu
----- Original Message -----
From: Pete Fritchman <petef@databits.net>
To: David Xu <bsddiy@163.net>
Sent: Thursday, May 10, 2001 1:17 AM
Subject: Re: kenel panic, vm_map_entry_create: kernel resources exhausted
> Cross-posting to both stable@ and questions@ is *BAD*.
>
> This is answered frequently. See /etc/login.conf for help on stopping
> fork bomb "attacks".
>
> -pete
>
> ++ 09/05/01 12:27 +0800 - David Xu:
> | I am using FreeBSD 4.3-STABLE, my machine has 64 RAM.
> | I can use a fork bomb to crash kernel under some conditions,
> | fork bomb program is:
> |
> | #include <unistd.h>
> | int main()
> | {
> | while(1)
> | {
> | if (fork() == 0)
> | break;
> | }
> | return 0;
> | }
> |
> | when kernel panic, it prints: vm_map_entry_create: kernel resources
> | exhausted,
> | then after some seconds, it reboots.
> |
> | I have found that if I use GENERIC kernel config, I can not trigger
this
> | bug,
> | default maxusers value in GENERIC kernel config file is 32, this is
fine,
> | if I change it to 128 and recompile/install kernel, I can use the fork
bomb
> | to
> | crash kernel. it seems this problem is RAM size and maxusers parameter
> | related. what max value of maxusers should I use if my RAM is 64M?
> |
> | ---
> | Regards,
> | David Xu
> |
> |
> |
> |
> | To Unsubscribe: send mail to majordomo@FreeBSD.org
> | with "unsubscribe freebsd-stable" in the body of the message
>
> --
> Pete Fritchman <petef@databits.net>
> Databits Network Services, Inc. <http://databits.net>;
> finger petef@databits.net for PGP key
>
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