Re: UVM and the NULL page

[Joerg Sonnenberger <joerg%bec.de@localhost>]

On Sat, Jul 30, 2016 at 11:12:57AM +0200, Maxime Villard wrote:
> This is something you generally don't need to remind people of, but I guess I'll
> have to here: you are neither my boss, nor my manager, nor my father, nor
> whoever. You don't get to tell me "find a different solution" with that tone,
> especially when it is clear you didn't try to make any effort to understand the
> issue.

Frankly, I find that reply to be completely out of line. NetBSD has a
long history of not stream rolling changes in. The onus of making sure
the change is acceptable is on you. There have been enough
justifications for the existing choices given. Whether the behavior is
buggy or not is a completely separate issue.

When you have been told to discuss changes to important parts of the
tree, it didn't mean "send a mail to tech-* and ignore the result".

> You know - as well as I do - that NULL pointer dereferences are quite common,
> and that it is the main way to execute malicious code in kernel mode. Allowing
> NULL is a huge problem on architectures like amd64. The way you are talking
> about compatibility sounds like you are ready to sacrifice the security of
> almost every NetBSD user just to allow a few programs that make use of a mapping
> model which has been known to be flawed for years. This is ridiculous.

No, the attitude of "security above usability" is ridiculous. Noone here
has disagreed with you that (void *)0 should never been accidentally
returned and more importantly, that the sysctl to guard this should
actually work. That it doesn't do it is a bug.

Joerg