On Mon, 23 Apr 2001, Peer-Christoph Mettelem wrote: hi, this is rather old. I posted similar program to Bugtraq years ago and the common thoughts by kernel developers were 'you can bring every unix to its knees when having shellaccess'. You can try to set limits, but there are a lot of resources which can be exhausted. To effectively prevent such 'attacks', use the "userdel" program which was wriiten for such purposes. Sebastian
Hi,
I just wrote a shell script which looks like this: while true do $0 done
I executed it as normal user and then the following happened: As you can imagine, very many shells were started (i wasnt able to count them because the system wasnt responding any more). And then the system started killing system processes like X and smbd. I got the following output on console 10: Apr 23 09:11:54 AlBundy kernel: VM: killing process kmail Apr 23 09:12:52 AlBundy kernel: VM: killing process smbd Apr 23 09:13:03 AlBundy kernel: VM: killing process smbd Apr 23 09:13:05 AlBundy kernel: VM: killing process xconsole Apr 23 09:13:13 AlBundy kernel: VM: killing process X
The system recovered itself by killing X. That worked because i started the script from a shell in KDE. But if the script would be started within a telnet session, it could be more dangerous.
I dont know if this is a security hole, but it might be.
My system: SuSE 7.0 (kernel 2.2.18) Lots of updates and patches installed PII 350 MHz 320 MB RAM
Peer-Christoph Mettelem BezRegMS (NRW, Germany) Software developer (trainee)
PS.: This is my first mail to the mailing list. Sorry if its OT or something...
-- ~ ~ perl self.pl ~ $_='print"\$_=\47$_\47;eval"';eval ~ krahmer@suse.de - SuSE Security Team ~