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SubjectRe: the new VM

On Tue, 26 Sep 2000, Pavel Machek wrote:

> Okay, I'm user on small machine and I'm doing stupid thing: I've got
> 6MB ram, and I keep inserting modules. I insert module_1mb.o. Then I
> insert module_1mb.o. Repeat. How does it end? I think that
> kmalloc(GFP_KERNEL) *has* to return NULL at some point.

if a stupid root user keeps inserting bogus modules :-) then thats a
problem, no matter what. I can DoS your system if given the right to
insert arbitrary size modules, even if kmalloc returns NULL. For such
things explicit highlevel protection is needed - completely independently
of the VM allocation issues. Returning NULL in kmalloc() is just a way to
say: 'oops, we screwed up somewhere'. And i'd suggest to not work around
such screwups by checking for NULL and trying to handle it. I suggest to
rather fix those screwups.

the __GFP_SOFT suggestion handles these things nicely.

Ingo

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