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Re: [f-cpu] TLB right



cedric a écrit :
> 
> Hi,
> 
>         I am back from vacation and I read some thing coming from scary movie. We
> must use 3 bits for right and that was an absolute requirement from the guy
> that work on the grsecurity patch. Never remove it, without them we will have
> some security problem.
>         The use of a special instruction to know if the pointer is a part of the
> kernel or not, mean that we need to change all the kernel exported function
> to verify in software if all the pointer are ok or not.

That's how things are done today. In 32 bits adresse space, kernel are
in 4-2 Go. So you could put the mask 0x7FFFFFFF to every pointer. So if
it's a kernel adresse, it will point elsewhere and die or it could
verify the last bit of the pointer if it's 1 it kill the process.

> So if we port an OS,
> we need to do a lot of change, and we can forget some of them (like the last
> local bug in OpenBSD).

Every kernel call should be check, so what ?

nicO

>         To conclude, I am for super user security bits and we need 3 "real" bits for
> security.
> 
> Cedric
> 
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