Protecting against kernel NULL-pointer derefs

[Dag-Erling Smørgrav]

Pieter de Boer <pieter at thedarkside.nl> writes:
> Given the amount of NULL-pointer dereference vulnerabilities in the
> FreeBSD kernel that have been discovered of late,

Specify "amount" and define "of late".

> By disallowing userland to map pages at address 0x0 (and a bit beyond),
> it is possible to make such NULL-pointer deref bugs mere DoS'es instead
> of code execution bugs. Linux has implemented such a protection for a
> long while now, by disallowing page mappings on 0x0 - 0xffff.

Yes, that really worked out great for them:

http://isc.sans.org/diary.html?storyid=6820

DES
-- 
Dag-Erling Smørgrav - des at des.no