Re: ext2 attribute immutable

H. Peter Anvin (
5 Apr 1996 09:28:15 GMT

Followup to: <>
By author: Zefram <>
In newsgroup:
> >> So, how does one need to modify /proc/1/mem to decrease the secure=
> >> after getting root access? :)
> >
> >You don't need to. You can just do a ptrace() on init, or create yo=
> >OWN init process --- by using a careful, controlled fork bomb we can
> >easily create new processes until we are about to wrap pid, then kil=
> >init and wait until one of our forks has a pid of 1.
> The fork attack shouldn't be possible. On SunOS, for example, when t=
> PIDs wrap, they wrap to 101, not 1. Doesn't Linux do something like
> this? If it wraps to 1, this has to change -- conceptually, low PIDs
> are a privileged resource, so access to them must be restricted.

Baloney. If init exits, the kernel will automatically spawn a new one
(Linux); most other OSes will treat init exiting as evidence of a
fatal crash and panic/reboot. Not only can't you kill init, but you
can't replace it by any less than changing the binary.


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