Subject: Re: Userland crashing the system
To: der Mouse <>
From: David Laight <>
List: tech-kern
Date: 11/25/2001 21:16:31
> > On the grounds that you shouldn't be able to crash the system from
> > user space if nothing else.....
> But where is the line between those and stuff like "dd if=/dev/zero
> of=/dev/mem"?  How do you draw that line between "if this crashes the
> kernel it's a bug that needs fixing" and "this is pilot error"?

Probably somewhere near 'I know what this command means' so it shouldn't
have that effect.

> As a nonprivileged user, I'd agree.  But as root, there are lots of
> foot-pointed pistols available.

Most of them are obvious - if you know what you typed means.

The best one I know of was many years ago on a pdp11 running RSX11M
(an OS not unlike unix in some respects).  On that system every part
of the disk was allocated to a file.  Someone, looking for extra space
of a full volume, found some big files in the 'hidden' directory and
deleted them to recover the space - deleting the 'inode table' and 
'allocation map' files had a slightly detrementel effect on the ability
to access data on the volume.....