> > Hi all, > > there is the program : [SNIP of wonderful reason to set rlimits] > > The idea is to take a lot of memory. So, we map all our virtual pages, > to force the system to allow all the pte (am talking about PC box). > So, the process will have allocated 768 pages that will never be > swapped (that's the crucial point). > > So, that's simple, you run this program as much time as you need to take > all the memory, and the PC won't be usable anymore (for my 64Mb box, > i need to run it about 20 times). > > And then, you can have a wonderful light-show with your HD-led :) (PC will > spend its time in swapping). > > How to solve it ? > Well, we could swap the pgd / pmd / pte, but i really don't know > if it is possible or what. The default TASK_SIZE is set in /usr/src/linux/include/asm/processor.h it is the virtual memory maximum map size. This in itself is not dynamically configurable (it really has nothing to do with resources). The main factor is RLIMIT_AS, defined in /usr/src/linux/include/asm/resource.h, it controls how much virtual memory that a process can map, mmap utilizes virtual memory. You can safely throttle people by running a program which calls setrlimit(2) with RLIMIT_AS as the resource. By far, 3GB is too much. This is only a DoS if you LET it be a DoS. > > If this bug is already well know, am sorry to disturb with it. > > It applies only on the 2.0 kernel, for the 2.1 (soon 2.2) i don't know > if it works, will have to read the source. > > Sed. > p6mip300at_private > > --Perry -- Perry Harrington System Software Engineer zelur xuniL () http://www.webcom.com perry.harringtonat_private Think Blue. /\
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